From 19da9c3cd8248e2d89ee6a938be9dfe55d601ca1 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Thu, 12 Aug 2021 12:04:43 +1000
Subject: [PATCH 01/36] Implement mail host fallback and DNS delivery, fix To
 address parsing, set SmtpOptions to use Lazy

---
 src/Seq.App.EmailPlus/DeliveryType.cs         |  12 ++
 src/Seq.App.EmailPlus/DirectMailGateway.cs    | 124 ++++++++++++++++--
 src/Seq.App.EmailPlus/DnsMailResult.cs        |  14 ++
 src/Seq.App.EmailPlus/EmailApp.cs             |  81 ++++++++++--
 src/Seq.App.EmailPlus/HandlebarsHelpers.cs    |   1 -
 src/Seq.App.EmailPlus/IMailGateway.cs         |   2 +-
 src/Seq.App.EmailPlus/MailResult.cs           |   6 +-
 .../Seq.App.EmailPlus.csproj                  |   1 +
 src/Seq.App.EmailPlus/SmtpOptions.cs          |  20 ++-
 .../EmailReactorTests.cs                      |  17 ++-
 .../Support/CollectingMailGateway.cs          |  10 +-
 .../Support/SentMessage.cs                    |   4 +-
 12 files changed, 254 insertions(+), 38 deletions(-)
 create mode 100644 src/Seq.App.EmailPlus/DeliveryType.cs
 create mode 100644 src/Seq.App.EmailPlus/DnsMailResult.cs

diff --git a/src/Seq.App.EmailPlus/DeliveryType.cs b/src/Seq.App.EmailPlus/DeliveryType.cs
new file mode 100644
index 0000000..ae985a5
--- /dev/null
+++ b/src/Seq.App.EmailPlus/DeliveryType.cs
@@ -0,0 +1,12 @@
+namespace Seq.App.EmailPlus
+{
+    public enum DeliveryType
+    {
+        MailHost,
+        MailFallback,
+        Dns,
+        DnsFallback,
+        HostDnsFallback,
+        None = -1
+    }
+}
diff --git a/src/Seq.App.EmailPlus/DirectMailGateway.cs b/src/Seq.App.EmailPlus/DirectMailGateway.cs
index 262b8bd..3df7c30 100644
--- a/src/Seq.App.EmailPlus/DirectMailGateway.cs
+++ b/src/Seq.App.EmailPlus/DirectMailGateway.cs
@@ -1,5 +1,9 @@
 using System;
+using System.Collections.Generic;
+using System.Linq;
 using System.Threading.Tasks;
+using DnsClient;
+using DnsClient.Protocol;
 using MailKit.Net.Smtp;
 using MimeKit;
 
@@ -7,25 +11,125 @@ namespace Seq.App.EmailPlus
 {
     class DirectMailGateway : IMailGateway
     {
+        readonly SmtpClient _client = new SmtpClient();
+
         public async Task<MailResult> Send(SmtpOptions options, MimeMessage message)
         {
             if (message == null) throw new ArgumentNullException(nameof(message));
+            var mailResult = new MailResult();
+            var type = DeliveryType.MailHost;
+            foreach (var server in options.ServerList)
+            {
+                mailResult = await TryDeliver(server, options, message, type);
+                if (!mailResult.Success)
+                    type = DeliveryType.MailFallback;
+                else
+                    break;
+            }
+
+            return mailResult;
+        }
+
+        public async Task<DnsMailResult> SendDns(DeliveryType deliveryType, SmtpOptions options, MimeMessage message)
+        {
+            var dnsResult = new DnsMailResult {Success = true};
+            var resultList = new List<MailResult>();
+            var lastServer = string.Empty;
+            if (message == null) throw new ArgumentNullException(nameof(message));
+            var type = deliveryType;
+
+            try
+            {
+                var domains = GetDomains(message);
+
+                var dnsClient = new LookupClient();
+                foreach (var domain in domains)
+                {
+                    type = deliveryType;
+                    lastServer = domain;
+                    var mx = await dnsClient.QueryAsync(domain, QueryType.MX);
+                    var mxServers =
+                        (from mxServer in mx.Answers
+                            where !string.IsNullOrEmpty(((MxRecord) mxServer).Exchange)
+                            select ((MxRecord) mxServer).Exchange).Select(dummy => (string) dummy).ToList();
+                    var mailResult = new MailResult();
+                    foreach (var server in mxServers)
+                    {
+                        lastServer = server;
+                        dnsResult.LastServer = server;
+                        dnsResult.Type = type;
+                        mailResult = await TryDeliver(server, options, message, type);
+                        resultList.Add(mailResult);
+
+                        if (mailResult.Success)
+                            break;
+                        type = DeliveryType.DnsFallback;
+                    }
+
+                    if (mailResult.Success) continue;
+                    dnsResult.LastServer = lastServer;
+                    dnsResult.Success = false;
+                    break;
+                }
+            }
+            catch (Exception ex)
+            {
+                dnsResult.Type = type;
+                dnsResult.LastServer = lastServer;
+                dnsResult.Success = false;
+                dnsResult.LastError = ex;
+            }
+
+            dnsResult.Results = resultList;
+            return dnsResult;
+        }
+
+
+        private static IEnumerable<string> GetDomains(MimeMessage message)
+        {
+            var domains = new List<string>();
+            foreach (var to in message.To)
+            {
+                var toDomain = to.ToString().Split('@')[1];
+                if (string.IsNullOrEmpty(toDomain)) continue;
+                foreach (var domain in domains.Where(domain =>
+                    !toDomain.Equals(domain, StringComparison.OrdinalIgnoreCase)))
+                {
+                    domains.Add(toDomain);
+                }
+            }
+
+            return domains;
+        }
+
+        private async Task<MailResult> TryDeliver(string server, SmtpOptions options, MimeMessage message,
+            DeliveryType deliveryType)
+        {
+            if (string.IsNullOrEmpty(server))
+                return new MailResult {Success = false, LastServer = server, Type = deliveryType};
             try
             {
-                var client = new SmtpClient();
-                
-                await client.ConnectAsync(options.Server, options.Port, options.SocketOptions);
-                if (options.RequiresAuthentication)
-                    await client.AuthenticateAsync(options.User, options.Password);
-                await client.SendAsync(message);
-                await client.DisconnectAsync(true);
-
-                return new MailResult {Success = true};
+                if (!string.IsNullOrEmpty(server))
+                {
+                    await _client.ConnectAsync(server, options.Port, options.SocketOptions);
+                    if (options.RequiresAuthentication)
+                        await _client.AuthenticateAsync(options.User, options.Password);
+                }
+                else
+                {
+                    var dnsClient = new LookupClient();
+                }
+
+                await _client.SendAsync(message);
+                await _client.DisconnectAsync(true);
+
+                return new MailResult {Success = true, LastServer = server, Type = deliveryType};
             }
             catch (Exception ex)
             {
-                return new MailResult {Success = false, Errors = ex};
+                return new MailResult {Success = false, Errors = ex, LastServer = server, Type = deliveryType};
             }
         }
+
     }
 }
\ No newline at end of file
diff --git a/src/Seq.App.EmailPlus/DnsMailResult.cs b/src/Seq.App.EmailPlus/DnsMailResult.cs
new file mode 100644
index 0000000..7aede1b
--- /dev/null
+++ b/src/Seq.App.EmailPlus/DnsMailResult.cs
@@ -0,0 +1,14 @@
+using System;
+using System.Collections.Generic;
+
+namespace Seq.App.EmailPlus
+{
+    public class DnsMailResult
+    {
+        public bool Success { get; set; }
+        public DeliveryType Type { get; set; }
+        public string LastServer { get; set; }
+        public Exception LastError { get; set; }
+        public List<MailResult> Results { get; set; }
+    }
+}
diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index 94e5f92..27302f3 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -3,10 +3,8 @@
 using System.Collections.Generic;
 using System.Dynamic;
 using System.Linq;
-using System.Net;
 using System.Threading.Tasks;
 using HandlebarsDotNet;
-using MailKit.Net.Smtp;
 using MailKit.Security;
 using MimeKit;
 using Seq.Apps;
@@ -25,7 +23,7 @@ public class EmailApp : SeqApp, ISubscribeToAsync<LogEventData>
         readonly IMailGateway _mailGateway = new DirectMailGateway();
         readonly ConcurrentDictionary<uint, DateTime> _lastSeen = new ConcurrentDictionary<uint, DateTime>();
         readonly Lazy<Template> _bodyTemplate, _subjectTemplate, _toAddressesTemplate;
-        readonly SmtpOptions _options;
+        public readonly Lazy<SmtpOptions> Options;
 
         const string DefaultSubjectTemplate = @"[{{$Level}}] {{{$Message}}} (via Seq)";
         const int MaxSubjectLength = 130;
@@ -43,16 +41,18 @@ internal EmailApp(IMailGateway mailGateway)
 
         public EmailApp()
         {
-            _options = _options = new SmtpOptions()
+            Options = new Lazy<SmtpOptions>(() => new SmtpOptions
             {
-                Server = Host, Port = Port ?? 25,
+                Server = Host,
+                DnsDelivery = DeliverUsingDns != null && (bool) DeliverUsingDns,
+                Port = Port ?? 25,
                 SocketOptions = EnableSsl != null && (bool) EnableSsl
                     ? SecureSocketOptions.SslOnConnect
                     : SecureSocketOptions.StartTlsWhenAvailable,
                 User = Username, Password = Password,
                 RequiresAuthentication = !string.IsNullOrEmpty(Username) && !string.IsNullOrEmpty(Password)
-            };
-            
+            });
+
             _subjectTemplate = new Lazy<Template>(() =>
             {
                 var subjectTemplate = SubjectTemplate;
@@ -95,9 +95,14 @@ public EmailApp()
         public string SubjectTemplate { get; set; }
 
         [SeqAppSetting(
-            HelpText = "The name of the SMTP server machine.")]
+            HelpText = "The name of the SMTP server machine. Optionally specify fallback hosts as comma-delimited string.",
+            IsOptional = true)]
         public new string Host { get; set; }
 
+        [SeqAppSetting(
+            HelpText = "Deliver directly using DNS. If Host is configured, this will be used as a fallback delivery mechanism.")]
+        public bool? DeliverUsingDns { get; set; }
+
         [SeqAppSetting(
             IsOptional = true,
             HelpText = "The port on the SMTP server machine to send mail to. Leave this blank to use the standard port (25).")]
@@ -148,20 +153,68 @@ public async Task OnAsync(Event<LogEventData> evt)
                 _lastSeen[evt.EventType] = DateTime.UtcNow;
             }
 
-            var to = FormatTemplate(_toAddressesTemplate.Value, evt, base.Host);
+            var to = FormatTemplate(_toAddressesTemplate.Value, evt, base.Host)
+                .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
+                .Select(t => t.Trim()).ToList();
             var body = FormatTemplate(_bodyTemplate.Value, evt, base.Host);
             var subject = FormatTemplate(_subjectTemplate.Value, evt, base.Host).Trim().Replace("\r", "")
                 .Replace("\n", "");
             if (subject.Length > MaxSubjectLength)
                 subject = subject.Substring(0, MaxSubjectLength);
 
-            var result = await _mailGateway.Send(_options, new MimeMessage(new List<InternetAddress> {MailboxAddress.Parse(From)},
-                new List<InternetAddress> {MailboxAddress.Parse(to)}, subject,
-                (new BodyBuilder() {HtmlBody = body}).ToMessageBody()));
+            var toList = to.Select(MailboxAddress.Parse).ToList();
+
+            var sent = false;
+            var type = DeliveryType.None;
+            var message = new MimeMessage(
+                new List<InternetAddress> {InternetAddress.Parse(From)},
+                toList, subject, (new BodyBuilder {HtmlBody = body}).ToMessageBody());
+
+            Exception lastError = null;
+            if (Options.Value.Server.Any())
+            {
+                type = DeliveryType.MailHost;
+                var result = await _mailGateway.Send(Options.Value, message);
+
+                sent = result.Success;
+                if (!result.Success)
+                {
+                    lastError = result.Errors;
+                    Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
+                        .ForContext("Success", sent).ForContext("Body", body)
+                        .ForContext(nameof(result.LastServer), result.LastServer)
+                        .ForContext(nameof(result.Type), result.Type).Error(result.Errors, "Error sending mail: ",
+                            result.Errors.Message);
+                }
+            }
 
-            if (!result.Success)
-                throw result.Errors;
+            if (!sent && Options.Value.DnsDelivery)
+            {
+                type = type == DeliveryType.None ? DeliveryType.Dns : DeliveryType.HostDnsFallback;
+                var result = await _mailGateway.SendDns(type, Options.Value, message);
+                sent = result.Success;
 
+                if (!result.Success)
+                {
+                    lastError = result.LastError;
+                    Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
+                        .ForContext("Success", sent).ForContext("Body", body)
+                        .ForContext(nameof(result.Results), result.Results, true)
+                        .ForContext(nameof(result.LastServer), result.LastServer).Error(result.LastError,
+                            "Error sending mail via DNS: ", result.LastError.Message);
+                }
+            }
+
+            switch (sent)
+            {
+                case false when lastError != null:
+                    throw lastError;
+                case true:
+                    Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
+                        .ForContext("Success", true).ForContext("Body", body)
+                        .Information("Mail Sent, From {From}, To: {To}, Subject: {Subject}");
+                    break;
+            }
         }
 
         public static string FormatTemplate(Template template, Event<LogEventData> evt, Host host)
diff --git a/src/Seq.App.EmailPlus/HandlebarsHelpers.cs b/src/Seq.App.EmailPlus/HandlebarsHelpers.cs
index fae0363..8a8cb3d 100644
--- a/src/Seq.App.EmailPlus/HandlebarsHelpers.cs
+++ b/src/Seq.App.EmailPlus/HandlebarsHelpers.cs
@@ -2,7 +2,6 @@
 using Newtonsoft.Json;
 using System;
 using System.Collections.Generic;
-using System.IO;
 using System.Linq;
 
 namespace Seq.App.EmailPlus
diff --git a/src/Seq.App.EmailPlus/IMailGateway.cs b/src/Seq.App.EmailPlus/IMailGateway.cs
index 40b0267..1daf4f2 100644
--- a/src/Seq.App.EmailPlus/IMailGateway.cs
+++ b/src/Seq.App.EmailPlus/IMailGateway.cs
@@ -1,7 +1,6 @@
 
 
 using System.Threading.Tasks;
-using MailKit.Net.Smtp;
 using MimeKit;
 
 namespace Seq.App.EmailPlus
@@ -9,5 +8,6 @@ namespace Seq.App.EmailPlus
     interface IMailGateway
     {
         Task<MailResult> Send(SmtpOptions options, MimeMessage message);
+        Task<DnsMailResult> SendDns(DeliveryType deliveryType, SmtpOptions options, MimeMessage message);
     }
 }
\ No newline at end of file
diff --git a/src/Seq.App.EmailPlus/MailResult.cs b/src/Seq.App.EmailPlus/MailResult.cs
index 6aa6fa1..ea0cf01 100644
--- a/src/Seq.App.EmailPlus/MailResult.cs
+++ b/src/Seq.App.EmailPlus/MailResult.cs
@@ -4,7 +4,9 @@ namespace Seq.App.EmailPlus
 {
     public class MailResult
     {
-        public bool Success;
-        public Exception Errors;
+        public bool Success { get; set; }
+        public DeliveryType Type { get; set; }
+        public string LastServer { get; set; }
+        public Exception Errors { get; set; }
     }
 }
\ No newline at end of file
diff --git a/src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj b/src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj
index f828d20..611a7e5 100644
--- a/src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj
+++ b/src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj
@@ -17,6 +17,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="DnsClient" Version="1.5.0" />
     <PackageReference Include="MailKit" Version="2.14.0" />
     <PackageReference Include="Seq.Apps" Version="5.1.0" />
     <PackageReference Include="Serilog" Version="2.10.0" />
diff --git a/src/Seq.App.EmailPlus/SmtpOptions.cs b/src/Seq.App.EmailPlus/SmtpOptions.cs
index c82921f..77bbb90 100644
--- a/src/Seq.App.EmailPlus/SmtpOptions.cs
+++ b/src/Seq.App.EmailPlus/SmtpOptions.cs
@@ -1,17 +1,31 @@
 using System;
 using System.Collections.Generic;
-using System.Text;
+using System.Linq;
 using MailKit.Security;
 
 namespace Seq.App.EmailPlus
 {
-    class SmtpOptions
+    public class SmtpOptions
     {
-        public string Server { get; set; } = string.Empty;
+        public string Server { get; set; }
+        public bool DnsDelivery { get; set; }
         public int Port { get; set; } = 25;
         public string User { get; set; } = string.Empty;
         public string Password { get; set; } = string.Empty;
         public bool RequiresAuthentication { get; set; }
         public SecureSocketOptions SocketOptions { get; set; }
+
+        public IEnumerable<string> ServerList
+        {
+            get
+            {
+                if (!string.IsNullOrEmpty(Server))
+                    return Server.Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
+                        .Select(t => t.Trim()).ToList();
+                return new List<string>();
+            }
+        }
     }
+
+    
 }
diff --git a/test/Seq.App.EmailPlus.Tests/EmailReactorTests.cs b/test/Seq.App.EmailPlus.Tests/EmailReactorTests.cs
index 8227950..a3bd63b 100644
--- a/test/Seq.App.EmailPlus.Tests/EmailReactorTests.cs
+++ b/test/Seq.App.EmailPlus.Tests/EmailReactorTests.cs
@@ -122,12 +122,25 @@ public async Task ToAddressesAreTemplated()
             };
 
             reactor.Attach(new TestAppHost());
-
             var data = Some.LogEvent(new Dictionary<string, object> { { "Name", "test" } });
             await reactor.OnAsync(data);
-
             var sent = mail.Sent.Single();
             Assert.Equal("test@example.com", sent.Message.To.ToString());
         }
+
+        [Fact]
+        public async Task SmtpOptionsCalculated()
+        {
+            var mail = new CollectingMailGateway();
+            var reactor = new EmailApp(mail)
+            {
+                From = "from@example.com",
+                To = "{{Name}}@example.com",
+                Host = "example.com,example2.com"
+            };
+
+            reactor.Attach(new TestAppHost());
+            Assert.True(reactor.Options.Value.ServerList.Count() == 2);
+        }
     }
 }
diff --git a/test/Seq.App.EmailPlus.Tests/Support/CollectingMailGateway.cs b/test/Seq.App.EmailPlus.Tests/Support/CollectingMailGateway.cs
index e16e3c6..72a92c5 100644
--- a/test/Seq.App.EmailPlus.Tests/Support/CollectingMailGateway.cs
+++ b/test/Seq.App.EmailPlus.Tests/Support/CollectingMailGateway.cs
@@ -1,6 +1,5 @@
 using System.Collections.Generic;
 using System.Threading.Tasks;
-using MailKit.Net.Smtp;
 using MimeKit;
 
 
@@ -14,7 +13,14 @@ public async Task<MailResult> Send(SmtpOptions options, MimeMessage message)
         {
             await Task.Run(() => Sent.Add(new SentMessage(message)));
             
-            return new MailResult() {Success = true};
+            return new MailResult {Success = true};
+        }
+
+        public async Task<DnsMailResult> SendDns(DeliveryType deliveryType, SmtpOptions options, MimeMessage message)
+        {
+            await Task.Run(() => Sent.Add(new SentMessage(message)));
+            
+            return new DnsMailResult {Success = true};
         }
     }
 }
diff --git a/test/Seq.App.EmailPlus.Tests/Support/SentMessage.cs b/test/Seq.App.EmailPlus.Tests/Support/SentMessage.cs
index ebd7712..4e1a6ee 100644
--- a/test/Seq.App.EmailPlus.Tests/Support/SentMessage.cs
+++ b/test/Seq.App.EmailPlus.Tests/Support/SentMessage.cs
@@ -1,6 +1,4 @@
-
-using MailKit.Net.Smtp;
-using MimeKit;
+using MimeKit;
 
 namespace Seq.App.EmailPlus.Tests.Support
 {

From 189f988831dd6ec27ca28032b68b80427dcaef1c Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Thu, 12 Aug 2021 12:07:31 +1000
Subject: [PATCH 02/36] Remove extant code from TryDeliver

---
 src/Seq.App.EmailPlus/DirectMailGateway.cs | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/src/Seq.App.EmailPlus/DirectMailGateway.cs b/src/Seq.App.EmailPlus/DirectMailGateway.cs
index 3df7c30..b997b0b 100644
--- a/src/Seq.App.EmailPlus/DirectMailGateway.cs
+++ b/src/Seq.App.EmailPlus/DirectMailGateway.cs
@@ -109,20 +109,15 @@ private async Task<MailResult> TryDeliver(string server, SmtpOptions options, Mi
                 return new MailResult {Success = false, LastServer = server, Type = deliveryType};
             try
             {
-                if (!string.IsNullOrEmpty(server))
-                {
-                    await _client.ConnectAsync(server, options.Port, options.SocketOptions);
-                    if (options.RequiresAuthentication)
-                        await _client.AuthenticateAsync(options.User, options.Password);
-                }
-                else
-                {
-                    var dnsClient = new LookupClient();
-                }
+                await _client.ConnectAsync(server, options.Port, options.SocketOptions);
+                if (options.RequiresAuthentication)
+                    await _client.AuthenticateAsync(options.User, options.Password);
+
 
                 await _client.SendAsync(message);
                 await _client.DisconnectAsync(true);
 
+
                 return new MailResult {Success = true, LastServer = server, Type = deliveryType};
             }
             catch (Exception ex)

From 1a45cc31e4ca10f8c7ede3c7b55bec5d9b3dab28 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Thu, 12 Aug 2021 12:16:58 +1000
Subject: [PATCH 03/36] Improve DnsMailResult logic

---
 src/Seq.App.EmailPlus/DirectMailGateway.cs    | 25 +++++++++++++------
 .../EmailReactorTests.cs                      |  2 +-
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/src/Seq.App.EmailPlus/DirectMailGateway.cs b/src/Seq.App.EmailPlus/DirectMailGateway.cs
index b997b0b..e99a134 100644
--- a/src/Seq.App.EmailPlus/DirectMailGateway.cs
+++ b/src/Seq.App.EmailPlus/DirectMailGateway.cs
@@ -32,7 +32,7 @@ public async Task<MailResult> Send(SmtpOptions options, MimeMessage message)
 
         public async Task<DnsMailResult> SendDns(DeliveryType deliveryType, SmtpOptions options, MimeMessage message)
         {
-            var dnsResult = new DnsMailResult {Success = true};
+            var dnsResult = new DnsMailResult();
             var resultList = new List<MailResult>();
             var lastServer = string.Empty;
             if (message == null) throw new ArgumentNullException(nameof(message));
@@ -56,9 +56,15 @@ public async Task<DnsMailResult> SendDns(DeliveryType deliveryType, SmtpOptions
                     foreach (var server in mxServers)
                     {
                         lastServer = server;
-                        dnsResult.LastServer = server;
-                        dnsResult.Type = type;
                         mailResult = await TryDeliver(server, options, message, type);
+                        dnsResult = new DnsMailResult()
+                        {
+                            LastServer = server,
+                            LastError = mailResult.Errors ?? mailResult.Errors,
+                            Type = type,
+                            Success = mailResult.Success
+                        };
+                        
                         resultList.Add(mailResult);
 
                         if (mailResult.Success)
@@ -67,17 +73,20 @@ public async Task<DnsMailResult> SendDns(DeliveryType deliveryType, SmtpOptions
                     }
 
                     if (mailResult.Success) continue;
-                    dnsResult.LastServer = lastServer;
                     dnsResult.Success = false;
+
                     break;
                 }
             }
             catch (Exception ex)
             {
-                dnsResult.Type = type;
-                dnsResult.LastServer = lastServer;
-                dnsResult.Success = false;
-                dnsResult.LastError = ex;
+                dnsResult = new DnsMailResult()
+                {
+                    Type = type,
+                    LastServer = lastServer,
+                    Success = false,
+                    LastError = ex
+                };
             }
 
             dnsResult.Results = resultList;
diff --git a/test/Seq.App.EmailPlus.Tests/EmailReactorTests.cs b/test/Seq.App.EmailPlus.Tests/EmailReactorTests.cs
index a3bd63b..e86cd43 100644
--- a/test/Seq.App.EmailPlus.Tests/EmailReactorTests.cs
+++ b/test/Seq.App.EmailPlus.Tests/EmailReactorTests.cs
@@ -129,7 +129,7 @@ public async Task ToAddressesAreTemplated()
         }
 
         [Fact]
-        public async Task SmtpOptionsCalculated()
+        public void SmtpOptionsCalculated()
         {
             var mail = new CollectingMailGateway();
             var reactor = new EmailApp(mail)

From bffb82a03db27afe9a6d1cde299461ea5b559745 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Thu, 12 Aug 2021 12:23:14 +1000
Subject: [PATCH 04/36] Retain lastError if not superseded

---
 src/Seq.App.EmailPlus/DirectMailGateway.cs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/Seq.App.EmailPlus/DirectMailGateway.cs b/src/Seq.App.EmailPlus/DirectMailGateway.cs
index e99a134..7174939 100644
--- a/src/Seq.App.EmailPlus/DirectMailGateway.cs
+++ b/src/Seq.App.EmailPlus/DirectMailGateway.cs
@@ -57,10 +57,11 @@ public async Task<DnsMailResult> SendDns(DeliveryType deliveryType, SmtpOptions
                     {
                         lastServer = server;
                         mailResult = await TryDeliver(server, options, message, type);
+                        var lastError = dnsResult.LastError;
                         dnsResult = new DnsMailResult()
                         {
                             LastServer = server,
-                            LastError = mailResult.Errors ?? mailResult.Errors,
+                            LastError = mailResult.Errors ?? lastError,
                             Type = type,
                             Success = mailResult.Success
                         };

From 26261af9990fb9c3dbd47a596a72a4d94b0e12c4 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Thu, 12 Aug 2021 12:42:30 +1000
Subject: [PATCH 05/36] Always track list of exceptions for logging

---
 src/Seq.App.EmailPlus/DirectMailGateway.cs | 28 ++++++++++++++--------
 src/Seq.App.EmailPlus/DnsMailResult.cs     |  3 ++-
 src/Seq.App.EmailPlus/EmailApp.cs          | 15 +++++++-----
 src/Seq.App.EmailPlus/MailResult.cs        |  4 +++-
 4 files changed, 32 insertions(+), 18 deletions(-)

diff --git a/src/Seq.App.EmailPlus/DirectMailGateway.cs b/src/Seq.App.EmailPlus/DirectMailGateway.cs
index 7174939..cd074fb 100644
--- a/src/Seq.App.EmailPlus/DirectMailGateway.cs
+++ b/src/Seq.App.EmailPlus/DirectMailGateway.cs
@@ -9,24 +9,31 @@
 
 namespace Seq.App.EmailPlus
 {
-    class DirectMailGateway : IMailGateway
+    internal class DirectMailGateway : IMailGateway
     {
-        readonly SmtpClient _client = new SmtpClient();
+        private readonly SmtpClient _client = new SmtpClient();
 
         public async Task<MailResult> Send(SmtpOptions options, MimeMessage message)
         {
             if (message == null) throw new ArgumentNullException(nameof(message));
             var mailResult = new MailResult();
             var type = DeliveryType.MailHost;
+            var errors = new List<Exception>();
             foreach (var server in options.ServerList)
             {
                 mailResult = await TryDeliver(server, options, message, type);
                 if (!mailResult.Success)
+                {
+                    errors.Add(mailResult.LastError);
                     type = DeliveryType.MailFallback;
+                }
                 else
+                {
                     break;
+                }
             }
 
+            mailResult.Errors = errors;
             return mailResult;
         }
 
@@ -35,6 +42,7 @@ public async Task<DnsMailResult> SendDns(DeliveryType deliveryType, SmtpOptions
             var dnsResult = new DnsMailResult();
             var resultList = new List<MailResult>();
             var lastServer = string.Empty;
+            var errors = new List<Exception>();
             if (message == null) throw new ArgumentNullException(nameof(message));
             var type = deliveryType;
 
@@ -58,14 +66,16 @@ public async Task<DnsMailResult> SendDns(DeliveryType deliveryType, SmtpOptions
                         lastServer = server;
                         mailResult = await TryDeliver(server, options, message, type);
                         var lastError = dnsResult.LastError;
-                        dnsResult = new DnsMailResult()
+                        errors.AddRange(mailResult.Errors);
+
+                        dnsResult = new DnsMailResult
                         {
                             LastServer = server,
-                            LastError = mailResult.Errors ?? lastError,
+                            LastError = mailResult.LastError ?? lastError,
                             Type = type,
                             Success = mailResult.Success
                         };
-                        
+
                         resultList.Add(mailResult);
 
                         if (mailResult.Success)
@@ -81,7 +91,7 @@ public async Task<DnsMailResult> SendDns(DeliveryType deliveryType, SmtpOptions
             }
             catch (Exception ex)
             {
-                dnsResult = new DnsMailResult()
+                dnsResult = new DnsMailResult
                 {
                     Type = type,
                     LastServer = lastServer,
@@ -90,6 +100,7 @@ public async Task<DnsMailResult> SendDns(DeliveryType deliveryType, SmtpOptions
                 };
             }
 
+            dnsResult.Errors = errors;
             dnsResult.Results = resultList;
             return dnsResult;
         }
@@ -104,9 +115,7 @@ private static IEnumerable<string> GetDomains(MimeMessage message)
                 if (string.IsNullOrEmpty(toDomain)) continue;
                 foreach (var domain in domains.Where(domain =>
                     !toDomain.Equals(domain, StringComparison.OrdinalIgnoreCase)))
-                {
                     domains.Add(toDomain);
-                }
             }
 
             return domains;
@@ -132,9 +141,8 @@ private async Task<MailResult> TryDeliver(string server, SmtpOptions options, Mi
             }
             catch (Exception ex)
             {
-                return new MailResult {Success = false, Errors = ex, LastServer = server, Type = deliveryType};
+                return new MailResult {Success = false, LastError = ex, LastServer = server, Type = deliveryType};
             }
         }
-
     }
 }
\ No newline at end of file
diff --git a/src/Seq.App.EmailPlus/DnsMailResult.cs b/src/Seq.App.EmailPlus/DnsMailResult.cs
index 7aede1b..a6994d5 100644
--- a/src/Seq.App.EmailPlus/DnsMailResult.cs
+++ b/src/Seq.App.EmailPlus/DnsMailResult.cs
@@ -9,6 +9,7 @@ public class DnsMailResult
         public DeliveryType Type { get; set; }
         public string LastServer { get; set; }
         public Exception LastError { get; set; }
-        public List<MailResult> Results { get; set; }
+        public List<Exception> Errors { get; set; } = new List<Exception>();
+        public List<MailResult> Results { get; set; } = new List<MailResult>();
     }
 }
diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index 27302f3..7ccface 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -171,20 +171,22 @@ public async Task OnAsync(Event<LogEventData> evt)
                 toList, subject, (new BodyBuilder {HtmlBody = body}).ToMessageBody());
 
             Exception lastError = null;
+            var errors = new List<Exception>();
             if (Options.Value.Server.Any())
             {
                 type = DeliveryType.MailHost;
                 var result = await _mailGateway.Send(Options.Value, message);
-
+                errors = result.Errors;
                 sent = result.Success;
                 if (!result.Success)
                 {
-                    lastError = result.Errors;
+                    lastError = result.LastError;
                     Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
                         .ForContext("Success", sent).ForContext("Body", body)
                         .ForContext(nameof(result.LastServer), result.LastServer)
-                        .ForContext(nameof(result.Type), result.Type).Error(result.Errors, "Error sending mail: ",
-                            result.Errors.Message);
+                        .ForContext(nameof(result.Type), result.Type).ForContext(nameof(result.Errors), result.Errors)
+                        .Error(result.LastError, "Error sending mail: ",
+                            result.LastError.Message);
                 }
             }
 
@@ -192,6 +194,7 @@ public async Task OnAsync(Event<LogEventData> evt)
             {
                 type = type == DeliveryType.None ? DeliveryType.Dns : DeliveryType.HostDnsFallback;
                 var result = await _mailGateway.SendDns(type, Options.Value, message);
+                errors = result.Errors;
                 sent = result.Success;
 
                 if (!result.Success)
@@ -199,7 +202,7 @@ public async Task OnAsync(Event<LogEventData> evt)
                     lastError = result.LastError;
                     Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
                         .ForContext("Success", sent).ForContext("Body", body)
-                        .ForContext(nameof(result.Results), result.Results, true)
+                        .ForContext(nameof(result.Results), result.Results, true).ForContext("Errors", errors)
                         .ForContext(nameof(result.LastServer), result.LastServer).Error(result.LastError,
                             "Error sending mail via DNS: ", result.LastError.Message);
                 }
@@ -211,7 +214,7 @@ public async Task OnAsync(Event<LogEventData> evt)
                     throw lastError;
                 case true:
                     Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
-                        .ForContext("Success", true).ForContext("Body", body)
+                        .ForContext("Success", true).ForContext("Body", body).ForContext("Errors", errors)
                         .Information("Mail Sent, From {From}, To: {To}, Subject: {Subject}");
                     break;
             }
diff --git a/src/Seq.App.EmailPlus/MailResult.cs b/src/Seq.App.EmailPlus/MailResult.cs
index ea0cf01..0bbf3af 100644
--- a/src/Seq.App.EmailPlus/MailResult.cs
+++ b/src/Seq.App.EmailPlus/MailResult.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 
 namespace Seq.App.EmailPlus
 {
@@ -7,6 +8,7 @@ public class MailResult
         public bool Success { get; set; }
         public DeliveryType Type { get; set; }
         public string LastServer { get; set; }
-        public Exception Errors { get; set; }
+        public Exception LastError { get; set; }
+        public List<Exception> Errors { get; set; } = new List<Exception>();
     }
 }
\ No newline at end of file

From 6c3f9f3fb3d7d50f26295fae75b37d9de3adc3d3 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Thu, 12 Aug 2021 14:41:27 +1000
Subject: [PATCH 06/36] Corrections from running mail host and DNS test cases

---
 src/Seq.App.EmailPlus/DirectMailGateway.cs    | 24 ++++----
 src/Seq.App.EmailPlus/EmailApp.cs             | 18 +++---
 src/Seq.App.EmailPlus/IMailGateway.cs         |  1 +
 .../EmailReactorTests.cs                      | 60 +++++++++++++++++++
 4 files changed, 84 insertions(+), 19 deletions(-)

diff --git a/src/Seq.App.EmailPlus/DirectMailGateway.cs b/src/Seq.App.EmailPlus/DirectMailGateway.cs
index cd074fb..b21c93d 100644
--- a/src/Seq.App.EmailPlus/DirectMailGateway.cs
+++ b/src/Seq.App.EmailPlus/DirectMailGateway.cs
@@ -11,7 +11,8 @@ namespace Seq.App.EmailPlus
 {
     internal class DirectMailGateway : IMailGateway
     {
-        private readonly SmtpClient _client = new SmtpClient();
+        static readonly SmtpClient Client = new SmtpClient();
+        static readonly LookupClient DnsClient = new LookupClient();
 
         public async Task<MailResult> Send(SmtpOptions options, MimeMessage message)
         {
@@ -50,12 +51,11 @@ public async Task<DnsMailResult> SendDns(DeliveryType deliveryType, SmtpOptions
             {
                 var domains = GetDomains(message);
 
-                var dnsClient = new LookupClient();
                 foreach (var domain in domains)
                 {
                     type = deliveryType;
                     lastServer = domain;
-                    var mx = await dnsClient.QueryAsync(domain, QueryType.MX);
+                    var mx = await DnsClient.QueryAsync(domain, QueryType.MX);
                     var mxServers =
                         (from mxServer in mx.Answers
                             where !string.IsNullOrEmpty(((MxRecord) mxServer).Exchange)
@@ -85,9 +85,12 @@ public async Task<DnsMailResult> SendDns(DeliveryType deliveryType, SmtpOptions
 
                     if (mailResult.Success) continue;
                     dnsResult.Success = false;
-
+                    if (dnsResult.LastError == null) dnsResult.LastError = mxServers.Count == 0 ? new Exception("DNS delivery failed - no MX records detected for " + domain) : new Exception("DNS delivery failed - no error detected");
                     break;
                 }
+
+                if (!domains.Any())
+                    dnsResult.LastError = new Exception("DNS delivery failed - no domains parsed from To addresses");
             }
             catch (Exception ex)
             {
@@ -106,15 +109,14 @@ public async Task<DnsMailResult> SendDns(DeliveryType deliveryType, SmtpOptions
         }
 
 
-        private static IEnumerable<string> GetDomains(MimeMessage message)
+        public static IEnumerable<string> GetDomains(MimeMessage message)
         {
             var domains = new List<string>();
             foreach (var to in message.To)
             {
                 var toDomain = to.ToString().Split('@')[1];
                 if (string.IsNullOrEmpty(toDomain)) continue;
-                foreach (var domain in domains.Where(domain =>
-                    !toDomain.Equals(domain, StringComparison.OrdinalIgnoreCase)))
+                if (!domains.Any(domain => domain.Equals(toDomain, StringComparison.OrdinalIgnoreCase)))
                     domains.Add(toDomain);
             }
 
@@ -128,13 +130,13 @@ private async Task<MailResult> TryDeliver(string server, SmtpOptions options, Mi
                 return new MailResult {Success = false, LastServer = server, Type = deliveryType};
             try
             {
-                await _client.ConnectAsync(server, options.Port, options.SocketOptions);
+                await Client.ConnectAsync(server, options.Port, options.SocketOptions);
                 if (options.RequiresAuthentication)
-                    await _client.AuthenticateAsync(options.User, options.Password);
+                    await Client.AuthenticateAsync(options.User, options.Password);
 
 
-                await _client.SendAsync(message);
-                await _client.DisconnectAsync(true);
+                await Client.SendAsync(message);
+                await Client.DisconnectAsync(true);
 
 
                 return new MailResult {Success = true, LastServer = server, Type = deliveryType};
diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index 7ccface..ec6289b 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -48,7 +48,7 @@ public EmailApp()
                 Port = Port ?? 25,
                 SocketOptions = EnableSsl != null && (bool) EnableSsl
                     ? SecureSocketOptions.SslOnConnect
-                    : SecureSocketOptions.StartTlsWhenAvailable,
+                    : SecureSocketOptions.None,
                 User = Username, Password = Password,
                 RequiresAuthentication = !string.IsNullOrEmpty(Username) && !string.IsNullOrEmpty(Password)
             });
@@ -172,7 +172,7 @@ public async Task OnAsync(Event<LogEventData> evt)
 
             Exception lastError = null;
             var errors = new List<Exception>();
-            if (Options.Value.Server.Any())
+            if (Options.Value.Server != null && Options.Value.Server.Any())
             {
                 type = DeliveryType.MailHost;
                 var result = await _mailGateway.Send(Options.Value, message);
@@ -180,13 +180,14 @@ public async Task OnAsync(Event<LogEventData> evt)
                 sent = result.Success;
                 if (!result.Success)
                 {
-                    lastError = result.LastError;
+                    if (result.LastError != null)
+                        lastError = result.LastError;
                     Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
                         .ForContext("Success", sent).ForContext("Body", body)
                         .ForContext(nameof(result.LastServer), result.LastServer)
                         .ForContext(nameof(result.Type), result.Type).ForContext(nameof(result.Errors), result.Errors)
-                        .Error(result.LastError, "Error sending mail: ",
-                            result.LastError.Message);
+                        .Error(result.LastError, "Error sending mail: {Message}, From: {From}, To: {To}, Subject: {Subject}",
+                            result.LastError?.Message, From, to, subject);
                 }
             }
 
@@ -199,12 +200,13 @@ public async Task OnAsync(Event<LogEventData> evt)
 
                 if (!result.Success)
                 {
-                    lastError = result.LastError;
+                    if (result.LastError != null)
+                        lastError = result.LastError;
                     Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
                         .ForContext("Success", sent).ForContext("Body", body)
                         .ForContext(nameof(result.Results), result.Results, true).ForContext("Errors", errors)
                         .ForContext(nameof(result.LastServer), result.LastServer).Error(result.LastError,
-                            "Error sending mail via DNS: ", result.LastError.Message);
+                            "Error sending mail via DNS: {Message}, From: {From}, To: {To}, Subject: {Subject}", result.LastError?.Message, From, to, subject);
                 }
             }
 
@@ -215,7 +217,7 @@ public async Task OnAsync(Event<LogEventData> evt)
                 case true:
                     Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
                         .ForContext("Success", true).ForContext("Body", body).ForContext("Errors", errors)
-                        .Information("Mail Sent, From {From}, To: {To}, Subject: {Subject}");
+                        .Information("Mail Sent, From: {From}, To: {To}, Subject: {Subject}");
                     break;
             }
         }
diff --git a/src/Seq.App.EmailPlus/IMailGateway.cs b/src/Seq.App.EmailPlus/IMailGateway.cs
index 1daf4f2..590cdbd 100644
--- a/src/Seq.App.EmailPlus/IMailGateway.cs
+++ b/src/Seq.App.EmailPlus/IMailGateway.cs
@@ -1,5 +1,6 @@
 
 
+using System.Collections.Generic;
 using System.Threading.Tasks;
 using MimeKit;
 
diff --git a/test/Seq.App.EmailPlus.Tests/EmailReactorTests.cs b/test/Seq.App.EmailPlus.Tests/EmailReactorTests.cs
index e86cd43..f9e062d 100644
--- a/test/Seq.App.EmailPlus.Tests/EmailReactorTests.cs
+++ b/test/Seq.App.EmailPlus.Tests/EmailReactorTests.cs
@@ -2,21 +2,30 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
+using MimeKit;
 using Seq.App.EmailPlus.Tests.Support;
 using Seq.Apps;
 using Seq.Apps.LogEvents;
 using Xunit;
+using Xunit.Abstractions;
 
 namespace Seq.App.EmailPlus.Tests
 {
     public class EmailReactorTests
     {
+        private readonly ITestOutputHelper _testOutputHelper;
+
         static EmailReactorTests()
         {
             // Ensure the handlebars helpers are registered.
             GC.KeepAlive(new EmailApp());
         }
 
+        public EmailReactorTests(ITestOutputHelper testOutputHelper)
+        {
+            _testOutputHelper = testOutputHelper;
+        }
+
         [Fact]
         public void BuiltInPropertiesAreRenderedInTemplates()
         {
@@ -142,5 +151,56 @@ public void SmtpOptionsCalculated()
             reactor.Attach(new TestAppHost());
             Assert.True(reactor.Options.Value.ServerList.Count() == 2);
         }
+
+        [Fact]
+        public void ParseDomainTest()
+        {
+            var mail = new DirectMailGateway();
+            var domains = DirectMailGateway.GetDomains(new MimeMessage(
+                new List<InternetAddress> {InternetAddress.Parse("test@example.com")},
+                new List<InternetAddress> {InternetAddress.Parse("test2@example.com"), InternetAddress.Parse("test3@example.com"), InternetAddress.Parse("test@example2.com")}, "Test",
+                (new BodyBuilder {HtmlBody = "test"}).ToMessageBody()));
+            Assert.True(domains.Count() == 2);
+        }
+
+        //[Fact]
+        //public async Task MailHostDeliveryTest()
+        //{
+        //    var reactor = new EmailApp()
+        //    {
+        //        Host = "fqdn",
+        //        EnableSsl = false,
+        //        From = "test@example.com",
+        //        To = "testdest@example.com",
+        //        BodyTemplate = "Test Body",
+        //        SubjectTemplate = "Test Email"
+        //    };
+
+        //    reactor.Attach(new TestAppHost());
+        //    var data = Some.LogEvent(new Dictionary<string, object> { { "Name", "test" } });
+        //    await reactor.OnAsync(data);
+
+        //}
+        
+        //[Fact]
+        //public async Task SmtpDnsDeliveryTest()
+        //{
+        //    var mail = new DirectMailGateway();
+        //    var reactor = new EmailApp(mail)
+        //    {
+        //        DeliverUsingDns = true,
+        //        EnableSsl = false,
+        //        From = "test@example.com",
+        //        To = "testdest@example.com",
+        //        BodyTemplate = "Test Body",
+        //        SubjectTemplate = "Test Email"
+        //    };
+
+        //    reactor.Attach(new TestAppHost());
+        //    var x = await mail.SendDns(DeliveryType.Dns, reactor.Options.Value, new MimeMessage(
+        //        new List<InternetAddress> {InternetAddress.Parse(reactor.From)},
+        //        new List<InternetAddress> {InternetAddress.Parse(reactor.To)}, reactor.SubjectTemplate, (new BodyBuilder {HtmlBody = reactor.BodyTemplate}).ToMessageBody()));
+        //    _testOutputHelper.WriteLine("{0}: {1}", x.Success, x.LastError);
+        //}
     }
 }

From e695402d04f85e891b0d9fe63f7fd4bdb0226016 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Fri, 13 Aug 2021 14:17:43 +1000
Subject: [PATCH 07/36] Add email priority and priority property mapping

---
 src/Seq.App.EmailPlus/EmailApp.cs      | 53 ++++++++++++++++++++++++++
 src/Seq.App.EmailPlus/EmailPriority.cs | 12 ++++++
 src/Seq.App.EmailPlus/SmtpOptions.cs   | 36 ++++++++++++++++-
 3 files changed, 99 insertions(+), 2 deletions(-)
 create mode 100644 src/Seq.App.EmailPlus/EmailPriority.cs

diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index ec6289b..e6e138a 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -46,6 +46,9 @@ public EmailApp()
                 Server = Host,
                 DnsDelivery = DeliverUsingDns != null && (bool) DeliverUsingDns,
                 Port = Port ?? 25,
+                Priority = SmtpOptions.ParsePriority(Priority, out var priorityMapping),
+                PriorityMapping = priorityMapping,
+                DefaultPriority = SmtpOptions.ParsePriority(DefaultPriority),
                 SocketOptions = EnableSsl != null && (bool) EnableSsl
                     ? SecureSocketOptions.SslOnConnect
                     : SecureSocketOptions.None,
@@ -122,6 +125,24 @@ public EmailApp()
                        "the default template that includes the message and properties (https://github.com/datalust/seq-apps/tree/master/src/Seq.App.EmailPlus/Resources/DefaultBodyTemplate.html).")]
         public string BodyTemplate { get; set; }
 
+        [SeqAppSetting(
+            IsOptional = true,
+            DisplayName = "Email Priority Property",
+            HelpText = "Event Property that can be used to map email priority; properties can be mapped to email priority using the Email Priority or Property Mapping field.")]
+        public string PriorityProperty { get; set; }
+        
+        [SeqAppSetting(
+            IsOptional = true,
+            DisplayName = "Email Priority or Property Mapping",
+            HelpText = "The Priority of the email - High, Normal, Low - Default Normal, or 'Email Priority Property' mapping using Property=Mapping format, eg. Highest=High,Error=Normal,Low=Low.")]
+        public string Priority { get; set; }
+
+        [SeqAppSetting(
+            IsOptional = true,
+            DisplayName = "Default Priority",
+            HelpText = "If using Email Priority mapping - Default for events not matching the mapping - High, Normal, or Low. Defaults to Normal.")]
+        public string DefaultPriority { get; set; }
+
         [SeqAppSetting(
             DisplayName = "Suppression time (minutes)",
             IsOptional = true,
@@ -170,6 +191,24 @@ public async Task OnAsync(Event<LogEventData> evt)
                 new List<InternetAddress> {InternetAddress.Parse(From)},
                 toList, subject, (new BodyBuilder {HtmlBody = body}).ToMessageBody());
 
+            switch (Options.Value.Priority)
+            {
+                case EmailPriority.UseMapping:
+                    if (!string.IsNullOrEmpty(PriorityProperty) && Options.Value.PriorityMapping.Count > 0 &&
+                        TryGetPropertyValueCI(evt.Data.Properties, PriorityProperty, out var priorityProperty) &&
+                        priorityProperty is string priorityValue &&
+                        Options.Value.PriorityMapping.TryGetValue(priorityValue, out var matchedPriority))
+                        message.Priority = (MessagePriority) matchedPriority;
+                    else
+                        message.Priority = (MessagePriority) Options.Value.DefaultPriority;
+                    break;
+                case EmailPriority.Low:
+                case EmailPriority.Normal:
+                case EmailPriority.High:
+                    message.Priority = (MessagePriority) Options.Value.Priority;
+                    break;
+            }
+
             Exception lastError = null;
             var errors = new List<Exception>();
             if (Options.Value.Server != null && Options.Value.Server.Any())
@@ -269,5 +308,19 @@ static object ToDynamic(object o)
 
             return o;
         }
+
+        static bool TryGetPropertyValueCI(IReadOnlyDictionary<string, object> properties, string propertyName,
+            out object propertyValue)
+        {
+            var pair = properties.FirstOrDefault(p => p.Key.Equals(propertyName, StringComparison.OrdinalIgnoreCase));
+            if (pair.Key == null)
+            {
+                propertyValue = null;
+                return false;
+            }
+
+            propertyValue = pair.Value;
+            return true;
+        }
     }
 }
diff --git a/src/Seq.App.EmailPlus/EmailPriority.cs b/src/Seq.App.EmailPlus/EmailPriority.cs
new file mode 100644
index 0000000..f0f44ad
--- /dev/null
+++ b/src/Seq.App.EmailPlus/EmailPriority.cs
@@ -0,0 +1,12 @@
+using MimeKit;
+
+namespace Seq.App.EmailPlus
+{
+    public enum EmailPriority
+    {
+        Low = MessagePriority.NonUrgent,
+        Normal = MessagePriority.Normal,
+        High = MessagePriority.Urgent,
+        UseMapping = -1,
+    }
+}
\ No newline at end of file
diff --git a/src/Seq.App.EmailPlus/SmtpOptions.cs b/src/Seq.App.EmailPlus/SmtpOptions.cs
index 77bbb90..3a4eceb 100644
--- a/src/Seq.App.EmailPlus/SmtpOptions.cs
+++ b/src/Seq.App.EmailPlus/SmtpOptions.cs
@@ -1,7 +1,9 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using HandlebarsDotNet.MemberAccessors;
 using MailKit.Security;
+using MimeKit;
 
 namespace Seq.App.EmailPlus
 {
@@ -13,6 +15,12 @@ public class SmtpOptions
         public string User { get; set; } = string.Empty;
         public string Password { get; set; } = string.Empty;
         public bool RequiresAuthentication { get; set; }
+
+        public EmailPriority Priority { get; set; } = EmailPriority.Normal;
+        public Dictionary<string, EmailPriority> PriorityMapping { get; set; } =
+            new Dictionary<string, EmailPriority>(StringComparer.OrdinalIgnoreCase);
+        public EmailPriority DefaultPriority { get; set; } = EmailPriority.Normal;
+
         public SecureSocketOptions SocketOptions { get; set; }
 
         public IEnumerable<string> ServerList
@@ -25,7 +33,31 @@ public IEnumerable<string> ServerList
                 return new List<string>();
             }
         }
-    }
 
-    
+        public static EmailPriority ParsePriority(string priority, out Dictionary<string,EmailPriority> priorityList)
+        {
+            priorityList = new Dictionary<string, EmailPriority>(StringComparer.OrdinalIgnoreCase);
+            if (string.IsNullOrEmpty(priority)) return EmailPriority.Normal;
+            if (!priority.Contains('='))
+                return Enum.TryParse(priority, out EmailPriority priorityValue) ? priorityValue : EmailPriority.Normal;
+            foreach (var kv in priority.Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
+                .Select(t => t.Trim()).ToList().Select(p => p.Split(new[] {'='}, StringSplitOptions.RemoveEmptyEntries).Select(t => t.Trim())
+                    .ToArray()))
+            {
+                if (kv.Length != 2 || !Enum.TryParse(kv[1], true, out EmailPriority value) ||
+                    value == EmailPriority.UseMapping) return EmailPriority.Normal;
+
+                priorityList.Add(kv[0], value);
+            }
+
+            return priorityList.Count > 0 ? EmailPriority.UseMapping : EmailPriority.Normal;
+
+        }
+
+        public static EmailPriority ParsePriority(string priority)
+        {
+            if (string.IsNullOrEmpty(priority)) return EmailPriority.Normal;
+            return Enum.TryParse(priority, out EmailPriority priorityValue) ? priorityValue : EmailPriority.Normal;
+        }
+    }
 }

From abf8d2586c8f75a51f574f069b9189d5504a25de Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Fri, 13 Aug 2021 14:49:09 +1000
Subject: [PATCH 08/36] Add cc, bcc, and plain text body

---
 src/Seq.App.EmailPlus/EmailApp.cs | 65 ++++++++++++++++++++++++++++++-
 1 file changed, 63 insertions(+), 2 deletions(-)

diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index e6e138a..2a845f8 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -22,7 +22,7 @@ public class EmailApp : SeqApp, ISubscribeToAsync<LogEventData>
     {
         readonly IMailGateway _mailGateway = new DirectMailGateway();
         readonly ConcurrentDictionary<uint, DateTime> _lastSeen = new ConcurrentDictionary<uint, DateTime>();
-        readonly Lazy<Template> _bodyTemplate, _subjectTemplate, _toAddressesTemplate;
+        readonly Lazy<Template> _bodyTemplate, _plainTextTemplate, _subjectTemplate, _toAddressesTemplate, _ccAddressesTemplate, _bccAddressesTemplate;
         public readonly Lazy<SmtpOptions> Options;
 
         const string DefaultSubjectTemplate = @"[{{$Level}}] {{{$Message}}} (via Seq)";
@@ -72,6 +72,14 @@ public EmailApp()
                 return Handlebars.Compile(bodyTemplate);
             });
 
+            _plainTextTemplate = new Lazy<Template>(() =>
+            {
+                var plainTextTemplate = PlainTextTemplate;
+                if (string.IsNullOrEmpty(plainTextTemplate))
+                    plainTextTemplate = Resources.DefaultBodyTemplate;
+                return Handlebars.Compile(plainTextTemplate);
+            });
+
             _toAddressesTemplate = new Lazy<Template>(() =>
             {
                 var toAddressTemplate = To;
@@ -79,6 +87,22 @@ public EmailApp()
                     return (_, __) => To;
                 return Handlebars.Compile(toAddressTemplate);
             });
+
+            _ccAddressesTemplate = new Lazy<Template>(() =>
+            {
+                var ccAddressTemplate = Cc;
+                if (string.IsNullOrEmpty(ccAddressTemplate))
+                    return (_, __) => To;
+                return Handlebars.Compile(ccAddressTemplate);
+            });
+
+            _bccAddressesTemplate = new Lazy<Template>(() =>
+            {
+                var bccAddressTemplate = Bcc;
+                if (string.IsNullOrEmpty(bccAddressTemplate))
+                    return (_, __) => To;
+                return Handlebars.Compile(bccAddressTemplate);
+            });
         }
 
         [SeqAppSetting(
@@ -91,6 +115,16 @@ public EmailApp()
             HelpText = "The account to which the email is being sent. Multiple addresses are separated by a comma. Handlebars syntax is supported.")]
         public string To { get; set; }
 
+        [SeqAppSetting(
+            DisplayName = "CC address",
+            HelpText = "The account to which emails should be sent as CC. Multiple addresses are separated by a comma. Handlebars syntax is supported.")]
+        public string Cc { get; set; }
+
+        [SeqAppSetting(
+            DisplayName = "BCC address",
+            HelpText = "The account to which the email is being sent as BCC. Multiple addresses are separated by a comma. Handlebars syntax is supported.")]
+        public string Bcc { get; set; }
+
         [SeqAppSetting(
             IsOptional = true,
             DisplayName = "Subject template",
@@ -125,6 +159,13 @@ public EmailApp()
                        "the default template that includes the message and properties (https://github.com/datalust/seq-apps/tree/master/src/Seq.App.EmailPlus/Resources/DefaultBodyTemplate.html).")]
         public string BodyTemplate { get; set; }
 
+        [SeqAppSetting(
+            IsOptional = true,
+            InputType = SettingInputType.LongText,
+            DisplayName = "Plain text template",
+            HelpText = "Optional plain text template to use when generating the email body, using Handlebars.NET syntax. Leave this blank if disable.")]
+        public string PlainTextTemplate { get; set; }
+
         [SeqAppSetting(
             IsOptional = true,
             DisplayName = "Email Priority Property",
@@ -177,20 +218,40 @@ public async Task OnAsync(Event<LogEventData> evt)
             var to = FormatTemplate(_toAddressesTemplate.Value, evt, base.Host)
                 .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
                 .Select(t => t.Trim()).ToList();
+
+            var cc = FormatTemplate(_ccAddressesTemplate.Value, evt, base.Host)
+                .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
+                .Select(t => t.Trim()).ToList();
+
+            var bcc = FormatTemplate(_bccAddressesTemplate.Value, evt, base.Host)
+                .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
+                .Select(t => t.Trim()).ToList();
+
             var body = FormatTemplate(_bodyTemplate.Value, evt, base.Host);
+            var textBody = FormatTemplate(_bodyTemplate.Value, evt, base.Host);
             var subject = FormatTemplate(_subjectTemplate.Value, evt, base.Host).Trim().Replace("\r", "")
                 .Replace("\n", "");
             if (subject.Length > MaxSubjectLength)
                 subject = subject.Substring(0, MaxSubjectLength);
 
             var toList = to.Select(MailboxAddress.Parse).ToList();
+            var ccList = cc.Select(MailboxAddress.Parse).ToList();
+            var bccList = bcc.Select(MailboxAddress.Parse).ToList();
 
             var sent = false;
             var type = DeliveryType.None;
             var message = new MimeMessage(
                 new List<InternetAddress> {InternetAddress.Parse(From)},
-                toList, subject, (new BodyBuilder {HtmlBody = body}).ToMessageBody());
+                toList, subject,
+                (new BodyBuilder
+                    {HtmlBody = body, TextBody = textBody == body ? string.Empty : textBody}).ToMessageBody());
+
+            if (ccList.Any())
+                message.Cc.AddRange(ccList);
 
+            if (bccList.Any())
+                message.Bcc.AddRange(bccList);
+            
             switch (Options.Value.Priority)
             {
                 case EmailPriority.UseMapping:

From 2a35adcde6c2d5109208d3984b2bdc5a49da171c Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Fri, 13 Aug 2021 15:18:48 +1000
Subject: [PATCH 09/36] Add replyTo, improved email logging

---
 src/Seq.App.EmailPlus/EmailApp.cs | 69 +++++++++++++++++++++----------
 1 file changed, 48 insertions(+), 21 deletions(-)

diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index 2a845f8..d2eabf1 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -22,7 +22,7 @@ public class EmailApp : SeqApp, ISubscribeToAsync<LogEventData>
     {
         readonly IMailGateway _mailGateway = new DirectMailGateway();
         readonly ConcurrentDictionary<uint, DateTime> _lastSeen = new ConcurrentDictionary<uint, DateTime>();
-        readonly Lazy<Template> _bodyTemplate, _plainTextTemplate, _subjectTemplate, _toAddressesTemplate, _ccAddressesTemplate, _bccAddressesTemplate;
+        readonly Lazy<Template> _bodyTemplate, _plainTextTemplate, _subjectTemplate, _toAddressesTemplate, _replyToAddressesTemplate, _ccAddressesTemplate, _bccAddressesTemplate;
         public readonly Lazy<SmtpOptions> Options;
 
         const string DefaultSubjectTemplate = @"[{{$Level}}] {{{$Message}}} (via Seq)";
@@ -83,25 +83,25 @@ public EmailApp()
             _toAddressesTemplate = new Lazy<Template>(() =>
             {
                 var toAddressTemplate = To;
-                if (string.IsNullOrEmpty(toAddressTemplate))
-                    return (_, __) => To;
-                return Handlebars.Compile(toAddressTemplate);
+                return string.IsNullOrEmpty(toAddressTemplate) ? (_, __) => To : Handlebars.Compile(toAddressTemplate);
+            });
+
+            _replyToAddressesTemplate = new Lazy<Template>(() =>
+            {
+                var replyToAddressTemplate = ReplyTo;
+                return string.IsNullOrEmpty(replyToAddressTemplate) ? (_, __) => ReplyTo : Handlebars.Compile(replyToAddressTemplate);
             });
 
             _ccAddressesTemplate = new Lazy<Template>(() =>
             {
                 var ccAddressTemplate = Cc;
-                if (string.IsNullOrEmpty(ccAddressTemplate))
-                    return (_, __) => To;
-                return Handlebars.Compile(ccAddressTemplate);
+                return string.IsNullOrEmpty(ccAddressTemplate) ? (_, __) => Cc : Handlebars.Compile(ccAddressTemplate);
             });
 
             _bccAddressesTemplate = new Lazy<Template>(() =>
             {
                 var bccAddressTemplate = Bcc;
-                if (string.IsNullOrEmpty(bccAddressTemplate))
-                    return (_, __) => To;
-                return Handlebars.Compile(bccAddressTemplate);
+                return string.IsNullOrEmpty(bccAddressTemplate) ? (_, __) => Bcc : Handlebars.Compile(bccAddressTemplate);
             });
         }
 
@@ -115,14 +115,22 @@ public EmailApp()
             HelpText = "The account to which the email is being sent. Multiple addresses are separated by a comma. Handlebars syntax is supported.")]
         public string To { get; set; }
 
+        [SeqAppSetting(
+            DisplayName = "ReplyTo address",
+            HelpText = "Optional account to which replies will be sent. Multiple addresses are separated by a comma. Handlebars syntax is supported.",
+            IsOptional = true)]
+        public string ReplyTo { get; set; }
+
         [SeqAppSetting(
             DisplayName = "CC address",
-            HelpText = "The account to which emails should be sent as CC. Multiple addresses are separated by a comma. Handlebars syntax is supported.")]
+            HelpText = "Optional account to which emails should be sent as CC. Multiple addresses are separated by a comma. Handlebars syntax is supported.",
+            IsOptional = true)]
         public string Cc { get; set; }
 
         [SeqAppSetting(
             DisplayName = "BCC address",
-            HelpText = "The account to which the email is being sent as BCC. Multiple addresses are separated by a comma. Handlebars syntax is supported.")]
+            HelpText = "Optional account to which the email is being sent as BCC. Multiple addresses are separated by a comma. Handlebars syntax is supported.",
+            IsOptional = true)]
         public string Bcc { get; set; }
 
         [SeqAppSetting(
@@ -219,6 +227,10 @@ public async Task OnAsync(Event<LogEventData> evt)
                 .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
                 .Select(t => t.Trim()).ToList();
 
+            var replyTo = FormatTemplate(_replyToAddressesTemplate.Value, evt, base.Host)
+                .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
+                .Select(t => t.Trim()).ToList();
+
             var cc = FormatTemplate(_ccAddressesTemplate.Value, evt, base.Host)
                 .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
                 .Select(t => t.Trim()).ToList();
@@ -234,6 +246,7 @@ public async Task OnAsync(Event<LogEventData> evt)
             if (subject.Length > MaxSubjectLength)
                 subject = subject.Substring(0, MaxSubjectLength);
 
+            var replyToList = replyTo.Select(MailboxAddress.Parse).ToList();
             var toList = to.Select(MailboxAddress.Parse).ToList();
             var ccList = cc.Select(MailboxAddress.Parse).ToList();
             var bccList = bcc.Select(MailboxAddress.Parse).ToList();
@@ -246,12 +259,16 @@ public async Task OnAsync(Event<LogEventData> evt)
                 (new BodyBuilder
                     {HtmlBody = body, TextBody = textBody == body ? string.Empty : textBody}).ToMessageBody());
 
+            if (replyToList.Any())
+                message.ReplyTo.AddRange(replyToList);
+
             if (ccList.Any())
                 message.Cc.AddRange(ccList);
 
             if (bccList.Any())
                 message.Bcc.AddRange(bccList);
-            
+
+            var priority = EmailPriority.Normal;
             switch (Options.Value.Priority)
             {
                 case EmailPriority.UseMapping:
@@ -259,17 +276,19 @@ public async Task OnAsync(Event<LogEventData> evt)
                         TryGetPropertyValueCI(evt.Data.Properties, PriorityProperty, out var priorityProperty) &&
                         priorityProperty is string priorityValue &&
                         Options.Value.PriorityMapping.TryGetValue(priorityValue, out var matchedPriority))
-                        message.Priority = (MessagePriority) matchedPriority;
+                        priority = matchedPriority;
                     else
-                        message.Priority = (MessagePriority) Options.Value.DefaultPriority;
+                        priority = Options.Value.DefaultPriority;
                     break;
                 case EmailPriority.Low:
                 case EmailPriority.Normal:
                 case EmailPriority.High:
-                    message.Priority = (MessagePriority) Options.Value.Priority;
+                    priority = Options.Value.Priority;
                     break;
             }
 
+            message.Priority = (MessagePriority) priority;
+
             Exception lastError = null;
             var errors = new List<Exception>();
             if (Options.Value.Server != null && Options.Value.Server.Any())
@@ -282,11 +301,14 @@ priorityProperty is string priorityValue &&
                 {
                     if (result.LastError != null)
                         lastError = result.LastError;
-                    Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
+                    Log.ForContext("From", From).ForContext("To", to)
+                        .ForContext("ReplyTo", replyTo).ForContext("CC", cc).ForContext("BCC", bcc)
+                        .ForContext("Priority", priority).ForContext("Subject", subject)
                         .ForContext("Success", sent).ForContext("Body", body)
                         .ForContext(nameof(result.LastServer), result.LastServer)
                         .ForContext(nameof(result.Type), result.Type).ForContext(nameof(result.Errors), result.Errors)
-                        .Error(result.LastError, "Error sending mail: {Message}, From: {From}, To: {To}, Subject: {Subject}",
+                        .Error(result.LastError,
+                            "Error sending mail: {Message}, From: {From}, To: {To}, Subject: {Subject}",
                             result.LastError?.Message, From, to, subject);
                 }
             }
@@ -302,11 +324,14 @@ priorityProperty is string priorityValue &&
                 {
                     if (result.LastError != null)
                         lastError = result.LastError;
-                    Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
+                    Log.ForContext("From", From).ForContext("To", to)
+                        .ForContext("ReplyTo", replyTo).ForContext("CC", cc).ForContext("BCC", bcc)
+                        .ForContext("Priority", priority).ForContext("Subject", subject)
                         .ForContext("Success", sent).ForContext("Body", body)
                         .ForContext(nameof(result.Results), result.Results, true).ForContext("Errors", errors)
                         .ForContext(nameof(result.LastServer), result.LastServer).Error(result.LastError,
-                            "Error sending mail via DNS: {Message}, From: {From}, To: {To}, Subject: {Subject}", result.LastError?.Message, From, to, subject);
+                            "Error sending mail via DNS: {Message}, From: {From}, To: {To}, Subject: {Subject}",
+                            result.LastError?.Message, From, to, subject);
                 }
             }
 
@@ -315,7 +340,9 @@ priorityProperty is string priorityValue &&
                 case false when lastError != null:
                     throw lastError;
                 case true:
-                    Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
+                    Log.ForContext("From", From).ForContext("To", to)
+                        .ForContext("ReplyTo", replyTo).ForContext("CC", cc).ForContext("BCC", bcc)
+                        .ForContext("Priority", priority).ForContext("Subject", subject)
                         .ForContext("Success", true).ForContext("Body", body).ForContext("Errors", errors)
                         .Information("Mail Sent, From: {From}, To: {To}, Subject: {Subject}");
                     break;

From 4b726fac9a52f9f707f16950b5183a955a90f9f8 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Tue, 17 Aug 2021 12:36:44 +1000
Subject: [PATCH 10/36] Merge with upstream conflicts

---
 src/Seq.App.EmailPlus/DirectMailGateway.cs    | 147 +++++++++++++++++-
 src/Seq.App.EmailPlus/EmailApp.cs             | 141 ++++++++++++-----
 src/Seq.App.EmailPlus/IMailGateway.cs         |   3 +-
 test/Seq.App.EmailPlus.Tests/EmailAppTests.cs |  28 ++++
 .../Support/CollectingMailGateway.cs          |  14 +-
 5 files changed, 285 insertions(+), 48 deletions(-)

diff --git a/src/Seq.App.EmailPlus/DirectMailGateway.cs b/src/Seq.App.EmailPlus/DirectMailGateway.cs
index cb00980..1b776da 100644
--- a/src/Seq.App.EmailPlus/DirectMailGateway.cs
+++ b/src/Seq.App.EmailPlus/DirectMailGateway.cs
@@ -1,5 +1,9 @@
 using System;
+using System.Collections.Generic;
+using System.Linq;
 using System.Threading.Tasks;
+using DnsClient;
+using DnsClient.Protocol;
 using MailKit.Net.Smtp;
 using MimeKit;
 
@@ -7,17 +11,144 @@ namespace Seq.App.EmailPlus
 {
     class DirectMailGateway : IMailGateway
     {
-        public async Task SendAsync(SmtpOptions options, MimeMessage message)
+        static readonly SmtpClient Client = new SmtpClient();
+        static readonly LookupClient DnsClient = new LookupClient();
+
+        public async Task<MailResult> SendAsync(SmtpOptions options, MimeMessage message)
         {
             if (message == null) throw new ArgumentNullException(nameof(message));
+            var mailResult = new MailResult();
+            var type = DeliveryType.MailHost;
+            var errors = new List<Exception>();
+            foreach (var server in options.ServerList)
+            {
+                mailResult = await TryDeliver(server, options, message, type);
+                if (!mailResult.Success)
+                {
+                    errors.Add(mailResult.LastError);
+                    type = DeliveryType.MailFallback;
+                }
+                else
+                {
+                    break;
+                }
+            }
+
+            mailResult.Errors = errors;
+            return mailResult;
+        }
+
+        public async Task<DnsMailResult> SendDnsAsync(DeliveryType deliveryType, SmtpOptions options,
+            MimeMessage message)
+        {
+            var dnsResult = new DnsMailResult();
+            var resultList = new List<MailResult>();
+            var lastServer = string.Empty;
+            var errors = new List<Exception>();
+            if (message == null) throw new ArgumentNullException(nameof(message));
+            var type = deliveryType;
+
+            try
+            {
+                var domains = GetDomains(message);
+
+                foreach (var domain in domains)
+                {
+                    type = deliveryType;
+                    lastServer = domain;
+                    var mx = await DnsClient.QueryAsync(domain, QueryType.MX);
+                    var mxServers =
+                        (from mxServer in mx.Answers
+                            where !string.IsNullOrEmpty(((MxRecord) mxServer).Exchange)
+                            select ((MxRecord) mxServer).Exchange).Select(dummy => (string) dummy).ToList();
+                    var mailResult = new MailResult();
+                    foreach (var server in mxServers)
+                    {
+                        lastServer = server;
+                        mailResult = await TryDeliver(server, options, message, type);
+                        var lastError = dnsResult.LastError;
+                        errors.AddRange(mailResult.Errors);
+
+                        dnsResult = new DnsMailResult
+                        {
+                            LastServer = server,
+                            LastError = mailResult.LastError ?? lastError,
+                            Type = type,
+                            Success = mailResult.Success
+                        };
+
+                        resultList.Add(mailResult);
+
+                        if (mailResult.Success)
+                            break;
+                        type = DeliveryType.DnsFallback;
+                    }
+
+                    if (mailResult.Success) continue;
+                    dnsResult.Success = false;
+                    if (dnsResult.LastError == null)
+                        dnsResult.LastError = mxServers.Count == 0
+                            ? new Exception("DNS delivery failed - no MX records detected for " + domain)
+                            : new Exception("DNS delivery failed - no error detected");
+                    break;
+                }
+
+                if (!domains.Any())
+                    dnsResult.LastError = new Exception("DNS delivery failed - no domains parsed from To addresses");
+            }
+            catch (Exception ex)
+            {
+                dnsResult = new DnsMailResult
+                {
+                    Type = type,
+                    LastServer = lastServer,
+                    Success = false,
+                    LastError = ex
+                };
+            }
+
+            dnsResult.Errors = errors;
+            dnsResult.Results = resultList;
+            return dnsResult;
+        }
+
+
+        public static IEnumerable<string> GetDomains(MimeMessage message)
+        {
+            var domains = new List<string>();
+            foreach (var to in message.To)
+            {
+                var toDomain = to.ToString().Split('@')[1];
+                if (string.IsNullOrEmpty(toDomain)) continue;
+                if (!domains.Any(domain => domain.Equals(toDomain, StringComparison.OrdinalIgnoreCase)))
+                    domains.Add(toDomain);
+            }
+
+            return domains;
+        }
+
+        private async Task<MailResult> TryDeliver(string server, SmtpOptions options, MimeMessage message,
+            DeliveryType deliveryType)
+        {
+            if (string.IsNullOrEmpty(server))
+                return new MailResult {Success = false, LastServer = server, Type = deliveryType};
+            try
+            {
+                await Client.ConnectAsync(server, options.Port, options.SocketOptions);
+                if (options.RequiresAuthentication)
+                    await Client.AuthenticateAsync(options.Username, options.Password);
+
+
+                await Client.SendAsync(message);
+                await Client.DisconnectAsync(true);
+
 
-            var client = new SmtpClient();
-                
-            await client.ConnectAsync(options.Server, options.Port, options.SocketOptions);
-            if (options.RequiresAuthentication)
-                await client.AuthenticateAsync(options.Username, options.Password);
-            await client.SendAsync(message);
-            await client.DisconnectAsync(true);
+                return new MailResult {Success = true, LastServer = server, Type = deliveryType};
+            }
+            catch (Exception ex)
+            {
+                return new MailResult {Success = false, LastError = ex, LastServer = server, Type = deliveryType};
+            }
         }
     }
 }
\ No newline at end of file
diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index a4bfbb1..0114853 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -23,7 +23,7 @@ public class EmailApp : SeqApp, ISubscribeToAsync<LogEventData>
         readonly IClock _clock;
         readonly Dictionary<uint, DateTime> _suppressions = new Dictionary<uint, DateTime>();
         readonly Lazy<Template> _bodyTemplate, _subjectTemplate, _toAddressesTemplate;
-        readonly SmtpOptions _options;
+        public readonly Lazy<SmtpOptions> Options;
 
         const string DefaultSubjectTemplate = @"[{{$Level}}] {{{$Message}}} (via Seq)";
         const int MaxSubjectLength = 130;
@@ -39,19 +39,19 @@ internal EmailApp(IMailGateway mailGateway, IClock clock)
             _clock = clock ?? throw new ArgumentNullException(nameof(clock));
 
             // ReSharper disable ExpressionIsAlwaysNull ConditionIsAlwaysTrueOrFalse
-            _options = _options = new SmtpOptions
+            Options = new Lazy<SmtpOptions>(() => new SmtpOptions
             {
                 Server = Host,
+                DnsDelivery = DeliverUsingDns != null && (bool) DeliverUsingDns,
                 Port = Port ?? 25,
-                SocketOptions = EnableSsl ?? false
+                SocketOptions = EnableSsl != null && (bool) EnableSsl
                     ? SecureSocketOptions.SslOnConnect
-                    : SecureSocketOptions.StartTlsWhenAvailable,
-                Username = Username,
-                Password = Password,
+                    : SecureSocketOptions.None,
+                Username = Username, Password = Password,
                 RequiresAuthentication = !string.IsNullOrEmpty(Username) && !string.IsNullOrEmpty(Password)
-            };
+            });
             // ReSharper restore ExpressionIsAlwaysNull ConditionIsAlwaysTrueOrFalse
-            
+
             _subjectTemplate = new Lazy<Template>(() =>
             {
                 var subjectTemplate = SubjectTemplate;
@@ -89,22 +89,32 @@ public EmailApp()
 
         [SeqAppSetting(
             DisplayName = "To address",
-            HelpText = "The account to which the email is being sent. Multiple addresses are separated by a comma. Handlebars syntax is supported.")]
+            HelpText =
+                "The account to which the email is being sent. Multiple addresses are separated by a comma. Handlebars syntax is supported.")]
         public string To { get; set; }
 
         [SeqAppSetting(
             IsOptional = true,
             DisplayName = "Subject template",
-            HelpText = "The subject of the email, using Handlebars syntax. If blank, a default subject will be generated.")]
+            HelpText =
+                "The subject of the email, using Handlebars syntax. If blank, a default subject will be generated.")]
         public string SubjectTemplate { get; set; }
 
         [SeqAppSetting(
-            HelpText = "The name of the SMTP server machine.")]
+            HelpText =
+                "The name of the SMTP server machine. Optionally specify fallback hosts as comma-delimited string.",
+            IsOptional = true)]
         public new string Host { get; set; }
 
+        [SeqAppSetting(
+            HelpText =
+                "Deliver directly using DNS. If Host is configured, this will be used as a fallback delivery mechanism.")]
+        public bool? DeliverUsingDns { get; set; }
+
         [SeqAppSetting(
             IsOptional = true,
-            HelpText = "The port on the SMTP server machine to send mail to. Leave this blank to use the standard port (25).")]
+            HelpText =
+                "The port on the SMTP server machine to send mail to. Leave this blank to use the standard port (25).")]
         public int? Port { get; set; }
 
         [SeqAppSetting(
@@ -117,8 +127,9 @@ public EmailApp()
             IsOptional = true,
             InputType = SettingInputType.LongText,
             DisplayName = "Body template",
-            HelpText = "The template to use when generating the email body, using Handlebars.NET syntax. Leave this blank to use " +
-                       "the default template that includes the message and properties (https://github.com/datalust/seq-apps/tree/master/src/Seq.App.EmailPlus/Resources/DefaultBodyTemplate.html).")]
+            HelpText =
+                "The template to use when generating the email body, using Handlebars.NET syntax. Leave this blank to use " +
+                "the default template that includes the message and properties (https://github.com/datalust/seq-apps/tree/master/src/Seq.App.EmailPlus/Resources/DefaultBodyTemplate.html).")]
         public string BodyTemplate { get; set; }
 
         [SeqAppSetting(
@@ -142,20 +153,74 @@ public async Task OnAsync(Event<LogEventData> evt)
         {
             if (ShouldSuppress(evt)) return;
 
-            var to = FormatTemplate(_toAddressesTemplate.Value, evt, base.Host);
+            var to = FormatTemplate(_toAddressesTemplate.Value, evt, base.Host)
+                .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
+                .Select(t => t.Trim()).ToList();
             var body = FormatTemplate(_bodyTemplate.Value, evt, base.Host);
             var subject = FormatTemplate(_subjectTemplate.Value, evt, base.Host).Trim().Replace("\r", "")
                 .Replace("\n", "");
             if (subject.Length > MaxSubjectLength)
                 subject = subject.Substring(0, MaxSubjectLength);
 
-            await _mailGateway.SendAsync(
-                _options,
-                new MimeMessage(
-                    new List<InternetAddress> {MailboxAddress.Parse(From)},
-                    new List<InternetAddress> {MailboxAddress.Parse(to)},
-                    subject,
-                    new BodyBuilder {HtmlBody = body}.ToMessageBody()));
+            var toList = to.Select(MailboxAddress.Parse).ToList();
+            var sent = false;
+            var type = DeliveryType.None;
+            var message = new MimeMessage(
+                new List<InternetAddress> {InternetAddress.Parse(From)},
+                toList, subject, (new BodyBuilder {HtmlBody = body}).ToMessageBody());
+
+            Exception lastError = null;
+            var errors = new List<Exception>();
+            if (Options.Value.Server != null && Options.Value.Server.Any())
+            {
+                type = DeliveryType.MailHost;
+                var result = await _mailGateway.SendAsync(Options.Value, message);
+                errors = result.Errors;
+                sent = result.Success;
+                if (!result.Success)
+                {
+                    if (result.LastError != null)
+                        lastError = result.LastError;
+                    Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
+                        .ForContext("Success", sent).ForContext("Body", body)
+                        .ForContext(nameof(result.LastServer), result.LastServer)
+                        .ForContext(nameof(result.Type), result.Type).ForContext(nameof(result.Errors), result.Errors)
+                        .Error(result.LastError,
+                            "Error sending mail: {Message}, From: {From}, To: {To}, Subject: {Subject}",
+                            result.LastError?.Message, From, to, subject);
+                }
+            }
+
+            if (!sent && Options.Value.DnsDelivery)
+            {
+                type = type == DeliveryType.None ? DeliveryType.Dns : DeliveryType.HostDnsFallback;
+                var result = await _mailGateway.SendDnsAsync(type, Options.Value, message);
+                errors = result.Errors;
+                sent = result.Success;
+
+                if (!result.Success)
+                {
+                    if (result.LastError != null)
+                        lastError = result.LastError;
+                    Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
+                        .ForContext("Success", sent).ForContext("Body", body)
+                        .ForContext(nameof(result.Results), result.Results, true).ForContext("Errors", errors)
+                        .ForContext(nameof(result.LastServer), result.LastServer).Error(result.LastError,
+                            "Error sending mail via DNS: {Message}, From: {From}, To: {To}, Subject: {Subject}",
+                            result.LastError?.Message, From, to, subject);
+                }
+            }
+
+            switch (sent)
+            {
+                case false when lastError != null:
+                    throw lastError;
+                case true:
+                    Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
+                        .ForContext("Success", true).ForContext("Body", body).ForContext("Errors", errors)
+                        .Information("Mail Sent, From: {From}, To: {To}, Subject: {Subject}");
+                    break;
+            }
         }
 
         bool ShouldSuppress(Event<LogEventData> evt)
@@ -189,23 +254,27 @@ bool ShouldSuppress(Event<LogEventData> evt)
 
         internal static string FormatTemplate(Template template, Event<LogEventData> evt, Host host)
         {
-            var properties = (IDictionary<string,object>) ToDynamic(evt.Data.Properties ?? new Dictionary<string, object>());
+            var properties =
+                (IDictionary<string, object>) ToDynamic(evt.Data.Properties ?? new Dictionary<string, object>());
 
-            var payload = (IDictionary<string,object>) ToDynamic(new Dictionary<string, object>
+            var payload = (IDictionary<string, object>) ToDynamic(new Dictionary<string, object>
             {
-                { "$Id",                  evt.Id },
-                { "$UtcTimestamp",        evt.TimestampUtc },
-                { "$LocalTimestamp",      evt.Data.LocalTimestamp },
-                { "$Level",               evt.Data.Level },
-                { "$MessageTemplate",     evt.Data.MessageTemplate },
-                { "$Message",             evt.Data.RenderedMessage },
-                { "$Exception",           evt.Data.Exception },
-                { "$Properties",          properties },
-                { "$EventType",           "$" + evt.EventType.ToString("X8") },
-                { "$Instance",            host.InstanceName },
-                { "$ServerUri",           host.BaseUri },
+                {"$Id", evt.Id},
+                {"$UtcTimestamp", evt.TimestampUtc},
+                {"$LocalTimestamp", evt.Data.LocalTimestamp},
+                {"$Level", evt.Data.Level},
+                {"$MessageTemplate", evt.Data.MessageTemplate},
+                {"$Message", evt.Data.RenderedMessage},
+                {"$Exception", evt.Data.Exception},
+                {"$Properties", properties},
+                {"$EventType", "$" + evt.EventType.ToString("X8")},
+                {"$Instance", host.InstanceName},
+                {"$ServerUri", host.BaseUri},
                 // Note, this will only be valid when events are streamed directly to the app, and not when the app is sending an alert notification.
-                { "$EventUri",            string.Concat(host.BaseUri, "#/events?filter=@Id%20%3D%20'", evt.Id, "'&amp;show=expanded") } 
+                {
+                    "$EventUri",
+                    string.Concat(host.BaseUri, "#/events?filter=@Id%20%3D%20'", evt.Id, "'&amp;show=expanded")
+                }
             });
 
             foreach (var property in properties)
diff --git a/src/Seq.App.EmailPlus/IMailGateway.cs b/src/Seq.App.EmailPlus/IMailGateway.cs
index ed599a2..6baa09a 100644
--- a/src/Seq.App.EmailPlus/IMailGateway.cs
+++ b/src/Seq.App.EmailPlus/IMailGateway.cs
@@ -5,6 +5,7 @@ namespace Seq.App.EmailPlus
 {
     interface IMailGateway
     {
-        Task SendAsync(SmtpOptions options, MimeMessage message);
+        Task<MailResult> SendAsync(SmtpOptions options, MimeMessage message);
+        Task<DnsMailResult> SendDnsAsync(DeliveryType deliveryType, SmtpOptions options, MimeMessage message);
     }
 }
\ No newline at end of file
diff --git a/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs b/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
index 0e387b8..7920290 100644
--- a/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
+++ b/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
@@ -1,6 +1,8 @@
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Threading.Tasks;
+using MimeKit;
 using Seq.App.EmailPlus.Tests.Support;
 using Seq.Apps;
 using Seq.Apps.LogEvents;
@@ -130,6 +132,32 @@ public async Task ToAddressesAreTemplated()
             Assert.Equal("test@example.com", sent.Message.To.ToString());
         }
 
+        [Fact]
+        public void SmtpOptionsCalculated()
+        {
+            var mail = new CollectingMailGateway();
+            var reactor = new EmailApp(mail, new SystemClock())
+            {
+                From = "from@example.com",
+                To = "{{Name}}@example.com",
+                Host = "example.com,example2.com"
+            };
+
+            reactor.Attach(new TestAppHost());
+            Assert.True(reactor.Options.Value.ServerList.Count() == 2);
+        }
+
+        [Fact]
+        public void ParseDomainTest()
+        {
+            var mail = new DirectMailGateway();
+            var domains = DirectMailGateway.GetDomains(new MimeMessage(
+                new List<InternetAddress> {InternetAddress.Parse("test@example.com")},
+                new List<InternetAddress> {InternetAddress.Parse("test2@example.com"), InternetAddress.Parse("test3@example.com"), InternetAddress.Parse("test@example2.com")}, "Test",
+                (new BodyBuilder {HtmlBody = "test"}).ToMessageBody()));
+            Assert.True(domains.Count() == 2);
+        }
+
         [Fact]
         public async Task EventsAreSuppressedWithinWindow()
         {
diff --git a/test/Seq.App.EmailPlus.Tests/Support/CollectingMailGateway.cs b/test/Seq.App.EmailPlus.Tests/Support/CollectingMailGateway.cs
index d5e2ac7..f3592cd 100644
--- a/test/Seq.App.EmailPlus.Tests/Support/CollectingMailGateway.cs
+++ b/test/Seq.App.EmailPlus.Tests/Support/CollectingMailGateway.cs
@@ -9,10 +9,18 @@ class CollectingMailGateway : IMailGateway
     {
         public List<SentMessage> Sent { get; } = new List<SentMessage>();
 
-        public Task SendAsync(SmtpOptions options, MimeMessage message)
+        public async Task<MailResult> SendAsync(SmtpOptions options, MimeMessage message)
         {
-            Sent.Add(new SentMessage(message));
-            return Task.CompletedTask;
+            await Task.Run(() => Sent.Add(new SentMessage(message)));
+            
+            return new MailResult {Success = true};
+        }
+
+        public async Task<DnsMailResult> SendDnsAsync(DeliveryType deliveryType, SmtpOptions options, MimeMessage message)
+        {
+            await Task.Run(() => Sent.Add(new SentMessage(message)));
+            
+            return new DnsMailResult {Success = true};
         }
     }
 }

From 7b74c41cd2e5d8386f5262d92cb4bddb5a09d207 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Tue, 17 Aug 2021 13:27:34 +1000
Subject: [PATCH 11/36] Handle self comments made on #81

---
 src/Seq.App.EmailPlus/EmailApp.cs    | 29 +++++++++++++++++-----------
 src/Seq.App.EmailPlus/SmtpOptions.cs | 20 +++++++++++++++++--
 2 files changed, 36 insertions(+), 13 deletions(-)

diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index 0114853..37521c5 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -44,9 +44,7 @@ internal EmailApp(IMailGateway mailGateway, IClock clock)
                 Server = Host,
                 DnsDelivery = DeliverUsingDns != null && (bool) DeliverUsingDns,
                 Port = Port ?? 25,
-                SocketOptions = EnableSsl != null && (bool) EnableSsl
-                    ? SecureSocketOptions.SslOnConnect
-                    : SecureSocketOptions.None,
+                SocketOptions = SmtpOptions.GetSocketOptions(EnableSsl, UseTlsWhenAvailable),
                 Username = Username, Password = Password,
                 RequiresAuthentication = !string.IsNullOrEmpty(Username) && !string.IsNullOrEmpty(Password)
             });
@@ -123,6 +121,12 @@ public EmailApp()
             HelpText = "Check this box if SSL is required to send email messages.")]
         public bool? EnableSsl { get; set; }
 
+        [SeqAppSetting(
+            IsOptional = true,
+            DisplayName = "Use Optional TLS",
+            HelpText = "If Enable SSL is disabled but the host supports TLS, allow Seq to use TLS.")]
+        public bool? UseTlsWhenAvailable { get; set; }
+
         [SeqAppSetting(
             IsOptional = true,
             InputType = SettingInputType.LongText,
@@ -164,6 +168,7 @@ public async Task OnAsync(Event<LogEventData> evt)
 
             var toList = to.Select(MailboxAddress.Parse).ToList();
             var sent = false;
+            var logged = false;
             var type = DeliveryType.None;
             var message = new MimeMessage(
                 new List<InternetAddress> {InternetAddress.Parse(From)},
@@ -188,6 +193,7 @@ public async Task OnAsync(Event<LogEventData> evt)
                         .Error(result.LastError,
                             "Error sending mail: {Message}, From: {From}, To: {To}, Subject: {Subject}",
                             result.LastError?.Message, From, to, subject);
+                    logged = true;
                 }
             }
 
@@ -208,19 +214,20 @@ public async Task OnAsync(Event<LogEventData> evt)
                         .ForContext(nameof(result.LastServer), result.LastServer).Error(result.LastError,
                             "Error sending mail via DNS: {Message}, From: {From}, To: {To}, Subject: {Subject}",
                             result.LastError?.Message, From, to, subject);
+                    logged = true;
                 }
             }
 
-            switch (sent)
+            if (sent)
             {
-                case false when lastError != null:
-                    throw lastError;
-                case true:
-                    Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
-                        .ForContext("Success", true).ForContext("Body", body).ForContext("Errors", errors)
-                        .Information("Mail Sent, From: {From}, To: {To}, Subject: {Subject}");
-                    break;
+                Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
+                    .ForContext("Success", true).ForContext("Body", body).ForContext("Errors", errors)
+                    .Information("Mail Sent, From: {From}, To: {To}, Subject: {Subject}");
             }
+            else if (!logged)
+                Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
+                    .ForContext("Success", true).ForContext("Body", body).ForContext("Errors", errors)
+                    .Error("Unhandled mail error, From: {From}, To: {To}, Subject: {Subject}");
         }
 
         bool ShouldSuppress(Event<LogEventData> evt)
diff --git a/src/Seq.App.EmailPlus/SmtpOptions.cs b/src/Seq.App.EmailPlus/SmtpOptions.cs
index 93eef42..603a26b 100644
--- a/src/Seq.App.EmailPlus/SmtpOptions.cs
+++ b/src/Seq.App.EmailPlus/SmtpOptions.cs
@@ -25,7 +25,23 @@ public IEnumerable<string> ServerList
                 return new List<string>();
             }
         }
-    }
 
-    
+        public static SecureSocketOptions GetSocketOptions(bool? EnableSsl, bool? UseTlsWhenAvailable)
+        {
+            if (EnableSsl != null)
+            {
+                switch (EnableSsl)
+                {
+                    case true:
+                        return SecureSocketOptions.SslOnConnect;
+                    case false when UseTlsWhenAvailable != null && !(bool) UseTlsWhenAvailable:
+                        return SecureSocketOptions.None;
+                    case false when UseTlsWhenAvailable != null && (bool) UseTlsWhenAvailable:
+                        return SecureSocketOptions.StartTlsWhenAvailable;
+                }
+            }
+
+            return SecureSocketOptions.Auto;
+        }
+    }
 }

From c2ad37eab9945f84a1bae4d74a2c0e57f7b64c00 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Tue, 17 Aug 2021 13:41:41 +1000
Subject: [PATCH 12/36] lastError local var no longer needed, update tests to
 reflect SecureSocketOptions results

---
 src/Seq.App.EmailPlus/EmailApp.cs             | 5 -----
 test/Seq.App.EmailPlus.Tests/EmailAppTests.cs | 5 +++++
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index 37521c5..a3f001c 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -174,7 +174,6 @@ public async Task OnAsync(Event<LogEventData> evt)
                 new List<InternetAddress> {InternetAddress.Parse(From)},
                 toList, subject, (new BodyBuilder {HtmlBody = body}).ToMessageBody());
 
-            Exception lastError = null;
             var errors = new List<Exception>();
             if (Options.Value.Server != null && Options.Value.Server.Any())
             {
@@ -184,8 +183,6 @@ public async Task OnAsync(Event<LogEventData> evt)
                 sent = result.Success;
                 if (!result.Success)
                 {
-                    if (result.LastError != null)
-                        lastError = result.LastError;
                     Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
                         .ForContext("Success", sent).ForContext("Body", body)
                         .ForContext(nameof(result.LastServer), result.LastServer)
@@ -206,8 +203,6 @@ public async Task OnAsync(Event<LogEventData> evt)
 
                 if (!result.Success)
                 {
-                    if (result.LastError != null)
-                        lastError = result.LastError;
                     Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
                         .ForContext("Success", sent).ForContext("Body", body)
                         .ForContext(nameof(result.Results), result.Results, true).ForContext("Errors", errors)
diff --git a/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs b/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
index 7920290..1e64089 100644
--- a/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
+++ b/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
+using MailKit.Security;
 using MimeKit;
 using Seq.App.EmailPlus.Tests.Support;
 using Seq.Apps;
@@ -145,6 +146,10 @@ public void SmtpOptionsCalculated()
 
             reactor.Attach(new TestAppHost());
             Assert.True(reactor.Options.Value.ServerList.Count() == 2);
+            Assert.True(SmtpOptions.GetSocketOptions(true, false) == SecureSocketOptions.SslOnConnect);
+            Assert.True(SmtpOptions.GetSocketOptions(false, false) == SecureSocketOptions.None);
+            Assert.True(SmtpOptions.GetSocketOptions(false, true) == SecureSocketOptions.StartTlsWhenAvailable);
+            Assert.True(SmtpOptions.GetSocketOptions(null, false) == SecureSocketOptions.Auto);
         }
 
         [Fact]

From 67db7462d62d1a69b929c7a0f247f0b93b4a3122 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Tue, 17 Aug 2021 13:50:29 +1000
Subject: [PATCH 13/36] Minor code issues from Resharper

---
 src/Seq.App.EmailPlus/DirectMailGateway.cs    |  4 ++--
 src/Seq.App.EmailPlus/DnsMailResult.cs        |  1 +
 src/Seq.App.EmailPlus/EmailApp.cs             |  1 -
 src/Seq.App.EmailPlus/SmtpOptions.cs          | 20 +++++++++----------
 .../Support/CollectingMailGateway.cs          |  1 -
 5 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/src/Seq.App.EmailPlus/DirectMailGateway.cs b/src/Seq.App.EmailPlus/DirectMailGateway.cs
index 1b776da..0d83245 100644
--- a/src/Seq.App.EmailPlus/DirectMailGateway.cs
+++ b/src/Seq.App.EmailPlus/DirectMailGateway.cs
@@ -50,7 +50,7 @@ public async Task<DnsMailResult> SendDnsAsync(DeliveryType deliveryType, SmtpOpt
 
             try
             {
-                var domains = GetDomains(message);
+                var domains = GetDomains(message).ToList();
 
                 foreach (var domain in domains)
                 {
@@ -127,7 +127,7 @@ public static IEnumerable<string> GetDomains(MimeMessage message)
             return domains;
         }
 
-        private async Task<MailResult> TryDeliver(string server, SmtpOptions options, MimeMessage message,
+        private static async Task<MailResult> TryDeliver(string server, SmtpOptions options, MimeMessage message,
             DeliveryType deliveryType)
         {
             if (string.IsNullOrEmpty(server))
diff --git a/src/Seq.App.EmailPlus/DnsMailResult.cs b/src/Seq.App.EmailPlus/DnsMailResult.cs
index a6994d5..3fc296d 100644
--- a/src/Seq.App.EmailPlus/DnsMailResult.cs
+++ b/src/Seq.App.EmailPlus/DnsMailResult.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+// ReSharper disable UnusedAutoPropertyAccessor.Global
 
 namespace Seq.App.EmailPlus
 {
diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index a3f001c..164ce68 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -4,7 +4,6 @@
 using System.Linq;
 using System.Threading.Tasks;
 using HandlebarsDotNet;
-using MailKit.Security;
 using MimeKit;
 using Seq.Apps;
 using Seq.Apps.LogEvents;
diff --git a/src/Seq.App.EmailPlus/SmtpOptions.cs b/src/Seq.App.EmailPlus/SmtpOptions.cs
index 603a26b..067ad61 100644
--- a/src/Seq.App.EmailPlus/SmtpOptions.cs
+++ b/src/Seq.App.EmailPlus/SmtpOptions.cs
@@ -26,19 +26,17 @@ public IEnumerable<string> ServerList
             }
         }
 
-        public static SecureSocketOptions GetSocketOptions(bool? EnableSsl, bool? UseTlsWhenAvailable)
+        public static SecureSocketOptions GetSocketOptions(bool? enableSsl, bool? useTlsWhenAvailable)
         {
-            if (EnableSsl != null)
+            if (enableSsl == null) return SecureSocketOptions.Auto;
+            switch (enableSsl)
             {
-                switch (EnableSsl)
-                {
-                    case true:
-                        return SecureSocketOptions.SslOnConnect;
-                    case false when UseTlsWhenAvailable != null && !(bool) UseTlsWhenAvailable:
-                        return SecureSocketOptions.None;
-                    case false when UseTlsWhenAvailable != null && (bool) UseTlsWhenAvailable:
-                        return SecureSocketOptions.StartTlsWhenAvailable;
-                }
+                case true:
+                    return SecureSocketOptions.SslOnConnect;
+                case false when useTlsWhenAvailable != null && !(bool) useTlsWhenAvailable:
+                    return SecureSocketOptions.None;
+                case false when useTlsWhenAvailable != null && (bool) useTlsWhenAvailable:
+                    return SecureSocketOptions.StartTlsWhenAvailable;
             }
 
             return SecureSocketOptions.Auto;
diff --git a/test/Seq.App.EmailPlus.Tests/Support/CollectingMailGateway.cs b/test/Seq.App.EmailPlus.Tests/Support/CollectingMailGateway.cs
index f3592cd..088e021 100644
--- a/test/Seq.App.EmailPlus.Tests/Support/CollectingMailGateway.cs
+++ b/test/Seq.App.EmailPlus.Tests/Support/CollectingMailGateway.cs
@@ -1,6 +1,5 @@
 using System.Collections.Generic;
 using System.Threading.Tasks;
-using MailKit.Net.Smtp;
 using MimeKit;
 
 namespace Seq.App.EmailPlus.Tests.Support

From 42864c6336eed1566168ac7287ae4b7606a12ea8 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Tue, 17 Aug 2021 14:26:03 +1000
Subject: [PATCH 14/36] Only need to parse list of servers once, handle no
 delivery methods being configured

---
 src/Seq.App.EmailPlus/DirectMailGateway.cs    |  2 +-
 src/Seq.App.EmailPlus/EmailApp.cs             | 16 ++++++++++++----
 src/Seq.App.EmailPlus/SmtpOptions.cs          | 15 ++++++---------
 test/Seq.App.EmailPlus.Tests/EmailAppTests.cs |  2 +-
 4 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/src/Seq.App.EmailPlus/DirectMailGateway.cs b/src/Seq.App.EmailPlus/DirectMailGateway.cs
index 0d83245..adda70e 100644
--- a/src/Seq.App.EmailPlus/DirectMailGateway.cs
+++ b/src/Seq.App.EmailPlus/DirectMailGateway.cs
@@ -20,7 +20,7 @@ public async Task<MailResult> SendAsync(SmtpOptions options, MimeMessage message
             var mailResult = new MailResult();
             var type = DeliveryType.MailHost;
             var errors = new List<Exception>();
-            foreach (var server in options.ServerList)
+            foreach (var server in options.Server)
             {
                 mailResult = await TryDeliver(server, options, message, type);
                 if (!mailResult.Success)
diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index 164ce68..96115f1 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -40,7 +40,7 @@ internal EmailApp(IMailGateway mailGateway, IClock clock)
             // ReSharper disable ExpressionIsAlwaysNull ConditionIsAlwaysTrueOrFalse
             Options = new Lazy<SmtpOptions>(() => new SmtpOptions
             {
-                Server = Host,
+                Server = SmtpOptions.GetServerList(Host).ToList(),
                 DnsDelivery = DeliverUsingDns != null && (bool) DeliverUsingDns,
                 Port = Port ?? 25,
                 SocketOptions = SmtpOptions.GetSocketOptions(EnableSsl, UseTlsWhenAvailable),
@@ -98,12 +98,14 @@ public EmailApp()
         public string SubjectTemplate { get; set; }
 
         [SeqAppSetting(
+            DisplayName = "SMTP Mail Host(s)",
             HelpText =
                 "The name of the SMTP server machine. Optionally specify fallback hosts as comma-delimited string.",
             IsOptional = true)]
         public new string Host { get; set; }
 
         [SeqAppSetting(
+            DisplayName = "Deliver using DNS",
             HelpText =
                 "Deliver directly using DNS. If Host is configured, this will be used as a fallback delivery mechanism.")]
         public bool? DeliverUsingDns { get; set; }
@@ -122,8 +124,8 @@ public EmailApp()
 
         [SeqAppSetting(
             IsOptional = true,
-            DisplayName = "Use Optional TLS",
-            HelpText = "If Enable SSL is disabled but the host supports TLS, allow Seq to use TLS.")]
+            DisplayName = "Use Optional TLS if available",
+            HelpText = "If Enable SSL is disabled but the host supports TLS, allow Seq to negotiate using TLS.")]
         public bool? UseTlsWhenAvailable { get; set; }
 
         [SeqAppSetting(
@@ -152,6 +154,12 @@ public EmailApp()
             HelpText = "The password to use when authenticating to the SMTP server, if required.")]
         public string Password { get; set; }
 
+        protected override void OnAttached()
+        {
+            if (string.IsNullOrEmpty(Host) && (DeliverUsingDns == null || !(bool) DeliverUsingDns))
+                throw new Exception("There are no delivery methods selected - you must specify at least one Host, or enable Deliver Using DNS");
+        }
+
         public async Task OnAsync(Event<LogEventData> evt)
         {
             if (ShouldSuppress(evt)) return;
@@ -171,7 +179,7 @@ public async Task OnAsync(Event<LogEventData> evt)
             var type = DeliveryType.None;
             var message = new MimeMessage(
                 new List<InternetAddress> {InternetAddress.Parse(From)},
-                toList, subject, (new BodyBuilder {HtmlBody = body}).ToMessageBody());
+                toList, subject, new BodyBuilder {HtmlBody = body}.ToMessageBody());
 
             var errors = new List<Exception>();
             if (Options.Value.Server != null && Options.Value.Server.Any())
diff --git a/src/Seq.App.EmailPlus/SmtpOptions.cs b/src/Seq.App.EmailPlus/SmtpOptions.cs
index 067ad61..cc931d3 100644
--- a/src/Seq.App.EmailPlus/SmtpOptions.cs
+++ b/src/Seq.App.EmailPlus/SmtpOptions.cs
@@ -7,7 +7,7 @@ namespace Seq.App.EmailPlus
 {
     public class SmtpOptions
     {
-        public string Server { get; set; }
+        public List<string> Server { get; set; } = new List<string>();
         public bool DnsDelivery { get; set; }
         public int Port { get; set; } = 25;
         public string Username { get; set; } = string.Empty;
@@ -15,15 +15,12 @@ public class SmtpOptions
         public bool RequiresAuthentication { get; set; }
         public SecureSocketOptions SocketOptions { get; set; }
 
-        public IEnumerable<string> ServerList
+        public static IEnumerable<string> GetServerList(string hostName)
         {
-            get
-            {
-                if (!string.IsNullOrEmpty(Server))
-                    return Server.Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
-                        .Select(t => t.Trim()).ToList();
-                return new List<string>();
-            }
+            if (!string.IsNullOrEmpty(hostName))
+                return hostName.Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
+                    .Select(t => t.Trim()).ToList();
+            return new List<string>();
         }
 
         public static SecureSocketOptions GetSocketOptions(bool? enableSsl, bool? useTlsWhenAvailable)
diff --git a/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs b/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
index 1e64089..9b3e8ba 100644
--- a/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
+++ b/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
@@ -145,7 +145,7 @@ public void SmtpOptionsCalculated()
             };
 
             reactor.Attach(new TestAppHost());
-            Assert.True(reactor.Options.Value.ServerList.Count() == 2);
+            Assert.True(reactor.Options.Value.Server.Count() == 2);
             Assert.True(SmtpOptions.GetSocketOptions(true, false) == SecureSocketOptions.SslOnConnect);
             Assert.True(SmtpOptions.GetSocketOptions(false, false) == SecureSocketOptions.None);
             Assert.True(SmtpOptions.GetSocketOptions(false, true) == SecureSocketOptions.StartTlsWhenAvailable);

From c0f99537f12081f7b880a1cd6e86cab1c72ebfed Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Tue, 17 Aug 2021 14:31:22 +1000
Subject: [PATCH 15/36] Update help text for clarity

---
 src/Seq.App.EmailPlus/EmailApp.cs | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index 96115f1..8a276e7 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -100,14 +100,14 @@ public EmailApp()
         [SeqAppSetting(
             DisplayName = "SMTP Mail Host(s)",
             HelpText =
-                "The name of the SMTP server machine. Optionally specify fallback hosts as comma-delimited string.",
+                "The name of the SMTP server machine. Optionally specify fallback hosts as comma-delimited string. If not specified, Deliver Using DNS should be enabled.",
             IsOptional = true)]
         public new string Host { get; set; }
 
         [SeqAppSetting(
             DisplayName = "Deliver using DNS",
             HelpText =
-                "Deliver directly using DNS. If Host is configured, this will be used as a fallback delivery mechanism.")]
+                "Deliver directly using DNS. If SMTP Mail Host(s) is configured, this will be used as a fallback delivery mechanism. If not enabled, SMTP Mail Host(s) should be configured.")]
         public bool? DeliverUsingDns { get; set; }
 
         [SeqAppSetting(
@@ -119,13 +119,13 @@ public EmailApp()
         [SeqAppSetting(
             IsOptional = true,
             DisplayName = "Enable SSL",
-            HelpText = "Check this box if SSL is required to send email messages.")]
+            HelpText = "Check this box if SSL is required to send email messages. If this is disabled, Use Optional TLS If Available can be configured to allow TLS to be used when offered.")]
         public bool? EnableSsl { get; set; }
 
         [SeqAppSetting(
             IsOptional = true,
             DisplayName = "Use Optional TLS if available",
-            HelpText = "If Enable SSL is disabled but the host supports TLS, allow Seq to negotiate using TLS.")]
+            HelpText = "If Enable SSL is disabled but the host supports TLS, allow Seq to negotiate using TLS. This has no effect if Enable SSL is enabled.")]
         public bool? UseTlsWhenAvailable { get; set; }
 
         [SeqAppSetting(
@@ -157,7 +157,7 @@ public EmailApp()
         protected override void OnAttached()
         {
             if (string.IsNullOrEmpty(Host) && (DeliverUsingDns == null || !(bool) DeliverUsingDns))
-                throw new Exception("There are no delivery methods selected - you must specify at least one Host, or enable Deliver Using DNS");
+                throw new Exception("There are no delivery methods selected - you must specify at least one SMTP Mail Host, or enable Deliver Using DNS");
         }
 
         public async Task OnAsync(Event<LogEventData> evt)

From fbf8a4fe28bfbe703209af15eac39692a6c2296d Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Wed, 18 Aug 2021 12:05:30 +1000
Subject: [PATCH 16/36] Adjust code for upstream changes

---
 src/Seq.App.EmailPlus/EmailApp.cs             | 22 +++++++++++--------
 src/Seq.App.EmailPlus/SmtpOptions.cs          |  2 +-
 test/Seq.App.EmailPlus.Tests/EmailAppTests.cs |  2 +-
 3 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index 39b0337..23107a3 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -38,14 +38,13 @@ internal EmailApp(IMailGateway mailGateway, IClock clock)
             _clock = clock ?? throw new ArgumentNullException(nameof(clock));
 
             // ReSharper disable ExpressionIsAlwaysNull ConditionIsAlwaysTrueOrFalse
-            Options = new Lazy<SmtpOptions>(() => new SmtpOptions(
+            _options = new Lazy<SmtpOptions>(() => new SmtpOptions(
                 Host,
                 DeliverUsingDns != null && (bool) DeliverUsingDns,
-                Port = Port ?? 25,
+                Port ?? 25,
                 SmtpOptions.GetSocketOptions(EnableSsl, UseTlsWhenAvailable),
-                Username, 
-                Password
-            });
+                Username,
+                Password));
             // ReSharper restore ExpressionIsAlwaysNull ConditionIsAlwaysTrueOrFalse
 
             _subjectTemplate = new Lazy<Template>(() =>
@@ -181,10 +180,10 @@ public async Task OnAsync(Event<LogEventData> evt)
                 toList, subject, new BodyBuilder {HtmlBody = body}.ToMessageBody());
 
             var errors = new List<Exception>();
-            if (Options.Value.Host != null && Options.Value.Host.Any())
+            if (_options.Value.Host != null && _options.Value.Host.Any())
             {
                 type = DeliveryType.MailHost;
-                var result = await _mailGateway.SendAsync(Options.Value, message);
+                var result = await _mailGateway.SendAsync(_options.Value, message);
                 errors = result.Errors;
                 sent = result.Success;
                 if (!result.Success)
@@ -200,10 +199,10 @@ public async Task OnAsync(Event<LogEventData> evt)
                 }
             }
 
-            if (!sent && Options.Value.DnsDelivery)
+            if (!sent && _options.Value.DnsDelivery)
             {
                 type = type == DeliveryType.None ? DeliveryType.Dns : DeliveryType.HostDnsFallback;
-                var result = await _mailGateway.SendDnsAsync(type, Options.Value, message);
+                var result = await _mailGateway.SendDnsAsync(type, _options.Value, message);
                 errors = result.Errors;
                 sent = result.Success;
 
@@ -311,5 +310,10 @@ static object ToDynamic(object o)
 
             return o;
         }
+
+        public SmtpOptions GetOptions()
+        {
+            return _options.Value;
+        }
     }
 }
diff --git a/src/Seq.App.EmailPlus/SmtpOptions.cs b/src/Seq.App.EmailPlus/SmtpOptions.cs
index 69861cf..5c171db 100644
--- a/src/Seq.App.EmailPlus/SmtpOptions.cs
+++ b/src/Seq.App.EmailPlus/SmtpOptions.cs
@@ -17,7 +17,7 @@ public class SmtpOptions
 
         public SmtpOptions(string host, bool dnsDelivery, int port, SecureSocketOptions socketOptions, string username = null, string password = null)
         {
-            Host = GetServerList(host);
+            Host = GetServerList(host).ToList();
             DnsDelivery = dnsDelivery;
             Port = port;
             Username = username;
diff --git a/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs b/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
index 9b3e8ba..5fcaea2 100644
--- a/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
+++ b/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
@@ -145,7 +145,7 @@ public void SmtpOptionsCalculated()
             };
 
             reactor.Attach(new TestAppHost());
-            Assert.True(reactor.Options.Value.Server.Count() == 2);
+            Assert.True(reactor.GetOptions().Host.Count() == 2);
             Assert.True(SmtpOptions.GetSocketOptions(true, false) == SecureSocketOptions.SslOnConnect);
             Assert.True(SmtpOptions.GetSocketOptions(false, false) == SecureSocketOptions.None);
             Assert.True(SmtpOptions.GetSocketOptions(false, true) == SecureSocketOptions.StartTlsWhenAvailable);

From e7bc50a9bc71e8d55ed9263c22f0f2a771378e8b Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Wed, 18 Aug 2021 12:50:56 +1000
Subject: [PATCH 17/36] GetServerList doesn't need to be public

---
 src/Seq.App.EmailPlus/SmtpOptions.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Seq.App.EmailPlus/SmtpOptions.cs b/src/Seq.App.EmailPlus/SmtpOptions.cs
index 5c171db..52f037e 100644
--- a/src/Seq.App.EmailPlus/SmtpOptions.cs
+++ b/src/Seq.App.EmailPlus/SmtpOptions.cs
@@ -25,7 +25,7 @@ public SmtpOptions(string host, bool dnsDelivery, int port, SecureSocketOptions
             SocketOptions = socketOptions;
         }
       
-        public IEnumerable<string> GetServerList(string hostName)
+        IEnumerable<string> GetServerList(string hostName)
         {
             if (!string.IsNullOrEmpty(hostName))
                 return hostName.Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)

From 6733a879d49148efa9f86626837040919aba6326 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Sun, 22 Aug 2021 14:22:01 +1000
Subject: [PATCH 18/36] Correct merge error and handle null replyTo/cc/bcc,
 resolve several Resharper code issues, add test case for envelope template
 parsing

---
 src/Seq.App.EmailPlus/EmailApp.cs             | 33 ++++++++++---------
 src/Seq.App.EmailPlus/SmtpOptions.cs          | 19 +++++------
 test/Seq.App.EmailPlus.Tests/EmailAppTests.cs | 25 ++++++++++++++
 3 files changed, 51 insertions(+), 26 deletions(-)

diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index a6f73c3..149e994 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -20,7 +20,7 @@ public class EmailApp : SeqApp, ISubscribeToAsync<LogEventData>
     {
         readonly IMailGateway _mailGateway;
         readonly IClock _clock;
-        readonly ConcurrentDictionary<uint, DateTime> _lastSeen = new ConcurrentDictionary<uint, DateTime>();
+        readonly Dictionary<uint, DateTime> _suppressions = new Dictionary<uint, DateTime>();
         readonly Lazy<Template> _bodyTemplate, _plainTextTemplate, _subjectTemplate, _toAddressesTemplate, _replyToAddressesTemplate, _ccAddressesTemplate, _bccAddressesTemplate;
         readonly Lazy<SmtpOptions> _options;
 
@@ -235,20 +235,20 @@ public async Task OnAsync(Event<LogEventData> evt)
                 .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
                 .Select(t => t.Trim()).ToList();
 
-            var replyTo = FormatTemplate(_replyToAddressesTemplate.Value, evt, base.Host)
+            var replyTo = string.IsNullOrEmpty(ReplyTo) ? new List<string>() : FormatTemplate(_replyToAddressesTemplate.Value, evt, base.Host)
                 .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
                 .Select(t => t.Trim()).ToList();
 
-            var cc = FormatTemplate(_ccAddressesTemplate.Value, evt, base.Host)
+            var cc = string.IsNullOrEmpty(Cc) ? new List<string>() : FormatTemplate(_ccAddressesTemplate.Value, evt, base.Host)
                 .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
                 .Select(t => t.Trim()).ToList();
 
-            var bcc = FormatTemplate(_bccAddressesTemplate.Value, evt, base.Host)
+            var bcc = string.IsNullOrEmpty(Bcc) ? new List<string>() : FormatTemplate(_bccAddressesTemplate.Value, evt, base.Host)
                 .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
                 .Select(t => t.Trim()).ToList();
 
             var body = FormatTemplate(_bodyTemplate.Value, evt, base.Host);
-            var textBody = FormatTemplate(_bodyTemplate.Value, evt, base.Host);
+            var textBody = FormatTemplate(_plainTextTemplate.Value, evt, base.Host);
             var subject = FormatTemplate(_subjectTemplate.Value, evt, base.Host).Trim().Replace("\r", "")
                 .Replace("\n", "");
             if (subject.Length > MaxSubjectLength)
@@ -264,8 +264,8 @@ public async Task OnAsync(Event<LogEventData> evt)
             var message = new MimeMessage(
                 new List<InternetAddress> {InternetAddress.Parse(From)},
                 toList, subject,
-                (new BodyBuilder
-                    {HtmlBody = body, TextBody = textBody == body ? string.Empty : textBody}).ToMessageBody());
+                new BodyBuilder
+                    {HtmlBody = body, TextBody = textBody == body ? string.Empty : textBody}.ToMessageBody());
 
             if (replyToList.Any())
                 message.ReplyTo.AddRange(replyToList);
@@ -277,21 +277,24 @@ public async Task OnAsync(Event<LogEventData> evt)
                 message.Bcc.AddRange(bccList);
 
             var priority = EmailPriority.Normal;
-            switch (Options.Value.Priority)
+            switch (_options.Value.Priority)
             {
                 case EmailPriority.UseMapping:
-                    if (!string.IsNullOrEmpty(PriorityProperty) && Options.Value.PriorityMapping.Count > 0 &&
+                    if (!string.IsNullOrEmpty(PriorityProperty) && _options.Value.PriorityMapping.Count > 0 &&
                         TryGetPropertyValueCI(evt.Data.Properties, PriorityProperty, out var priorityProperty) &&
                         priorityProperty is string priorityValue &&
-                        Options.Value.PriorityMapping.TryGetValue(priorityValue, out var matchedPriority))
+                        _options.Value.PriorityMapping.TryGetValue(priorityValue, out var matchedPriority))
                         priority = matchedPriority;
                     else
-                        priority = Options.Value.DefaultPriority;
+                        priority = _options.Value.DefaultPriority;
                     break;
                 case EmailPriority.Low:
                 case EmailPriority.Normal:
                 case EmailPriority.High:
-                    priority = Options.Value.Priority;
+                    priority = _options.Value.Priority;
+                    break;
+                default:
+                    priority = EmailPriority.Normal;
                     break;
             }
 
@@ -331,7 +334,7 @@ priorityProperty is string priorityValue &&
                         .ForContext("ReplyTo", replyTo).ForContext("CC", cc).ForContext("BCC", bcc)
                         .ForContext("Priority", priority).ForContext("Subject", subject)
                         .ForContext("Success", sent).ForContext("Body", body)
-                        .ForContext(nameof(result.Results), result.Results, true).ForContext("Errors", errors)
+                        .ForContext(nameof(result.Results), result.Results, true).ForContext("Errors", result.Errors)
                         .ForContext(nameof(result.LastServer), result.LastServer).Error(result.LastError,
                             "Error sending mail via DNS: {Message}, From: {From}, To: {To}, Subject: {Subject}",
                             result.LastError?.Message, From, to, subject);
@@ -345,14 +348,14 @@ priorityProperty is string priorityValue &&
                         .ForContext("ReplyTo", replyTo).ForContext("CC", cc).ForContext("BCC", bcc)
                         .ForContext("Priority", priority).ForContext("Subject", subject)
                         .ForContext("Success", true).ForContext("Body", body).ForContext("Errors", errors)
-                        .Information("Mail Sent, From: {From}, To: {To}, Subject: {Subject}");
+                        .Information("Mail Sent, From: {From}, To: {To}, Subject: {Subject}", From, to, subject);
             }
             else if (!logged)
                 Log.ForContext("From", From).ForContext("To", to)                        
 				.ForContext("ReplyTo", replyTo).ForContext("CC", cc).ForContext("BCC", bcc)
                 .ForContext("Priority", priority).ForContext("Subject", subject)
                 .ForContext("Success", true).ForContext("Body", body).ForContext("Errors", errors)
-                .Error("Unhandled mail error, From: {From}, To: {To}, Subject: {Subject}");
+                .Error("Unhandled mail error, From: {From}, To: {To}, Subject: {Subject}", From, to, subject);
         }
 
         bool ShouldSuppress(Event<LogEventData> evt)
diff --git a/src/Seq.App.EmailPlus/SmtpOptions.cs b/src/Seq.App.EmailPlus/SmtpOptions.cs
index da9e887..745bc73 100644
--- a/src/Seq.App.EmailPlus/SmtpOptions.cs
+++ b/src/Seq.App.EmailPlus/SmtpOptions.cs
@@ -1,24 +1,21 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using HandlebarsDotNet.MemberAccessors;
 using MailKit.Security;
-using MimeKit;
 
 namespace Seq.App.EmailPlus
 {
     public class SmtpOptions
     {
-        public List<string> Host { get; set; } = new List<string>();
+        public List<string> Host { get; set; }
         public bool DnsDelivery { get; set; }
-        public int Port { get; set; } = 25;
-        public string Username { get; set; } = string.Empty;
-        public string Password { get; set; } = string.Empty;
+        public int Port { get; set; }
+        public string Username { get; set; }
+        public string Password { get; set; }
         public bool RequiresAuthentication => !string.IsNullOrEmpty(Username) && !string.IsNullOrEmpty(Password);
-        public EmailPriority Priority { get; set; } = EmailPriority.Normal;
-        public Dictionary<string, EmailPriority> PriorityMapping { get; set; } =
-            new Dictionary<string, EmailPriority>(StringComparer.OrdinalIgnoreCase);
-        public EmailPriority DefaultPriority { get; set; } = EmailPriority.Normal;
+        public EmailPriority Priority { get; set; }
+        public Dictionary<string, EmailPriority> PriorityMapping { get; set; }
+        public EmailPriority DefaultPriority { get; set; }
         public SecureSocketOptions SocketOptions { get; set; }
 
         public SmtpOptions(string host, bool dnsDelivery, int port, string priority, string defaultPriority, SecureSocketOptions socketOptions, string username = null, string password = null)
@@ -34,7 +31,7 @@ public SmtpOptions(string host, bool dnsDelivery, int port, string priority, str
             SocketOptions = socketOptions;
         }
       
-        IEnumerable<string> GetServerList(string hostName)
+        static IEnumerable<string> GetServerList(string hostName)
         {
             if (!string.IsNullOrEmpty(hostName))
                 return hostName.Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
diff --git a/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs b/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
index 5fcaea2..3adf14c 100644
--- a/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
+++ b/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
@@ -133,6 +133,31 @@ public async Task ToAddressesAreTemplated()
             Assert.Equal("test@example.com", sent.Message.To.ToString());
         }
 
+        [Fact]
+        public async Task OptionalAddressesAreTemplated()
+        {
+            var mail = new CollectingMailGateway();
+            var app = new EmailApp(mail, new SystemClock())
+            {
+                From = "from@example.com",
+                ReplyTo = "{{Name}}@example.com",
+                To = "{{Name}}@example.com",
+                Cc = "{{Name}}@example.com",
+                Bcc = "{{Name}}@example.com",
+                Host = "example.com"
+            };
+
+            app.Attach(new TestAppHost());
+
+            var data = Some.LogEvent(includedProperties: new Dictionary<string, object> { { "Name", "test" } });
+            await app.OnAsync(data);
+
+            var sent = Assert.Single(mail.Sent);
+            Assert.Equal("test@example.com", sent.Message.ReplyTo.ToString());
+            Assert.Equal("test@example.com", sent.Message.Cc.ToString());
+            Assert.Equal("test@example.com", sent.Message.Bcc.ToString());
+        }
+
         [Fact]
         public void SmtpOptionsCalculated()
         {

From 72cec0b043c63c2905936505ad7636d917fe3e07 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Sat, 28 Aug 2021 09:34:34 +1000
Subject: [PATCH 19/36] Harmonise #86 with delivery enhancements

---
 src/Seq.App.EmailPlus/EmailApp.cs             |  9 ++-------
 src/Seq.App.EmailPlus/SmtpOptions.cs          |  6 ++++--
 test/Seq.App.EmailPlus.Tests/EmailAppTests.cs | 17 +++++------------
 3 files changed, 11 insertions(+), 21 deletions(-)

diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index 2f2ee35..ecea603 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -74,11 +74,6 @@ internal EmailApp(IMailGateway mailGateway, IClock clock)
             });
         }
 
-        internal static SecureSocketOptions RequireSslForPort(int port)
-        {
-            return (port == DefaultSslPort ? SecureSocketOptions.SslOnConnect : SecureSocketOptions.StartTls);
-        }
-
         public EmailApp()
             : this(new DirectMailGateway(), new SystemClock())
         {
@@ -174,9 +169,9 @@ public async Task OnAsync(Event<LogEventData> evt)
                 .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
                 .Select(t => t.Trim()).ToList();
 
-            if (to.Length == 0)
+            if (to.Count == 0)
             {
-                Log.Warning("Email 'to' address template did not evaluate to one or more recipient addresses");
+                Log.Error("Email 'to' address template did not evaluate to one or more recipient addresses - email cannot be sent!");
                 return;
             }
 
diff --git a/src/Seq.App.EmailPlus/SmtpOptions.cs b/src/Seq.App.EmailPlus/SmtpOptions.cs
index 52f037e..82f23e9 100644
--- a/src/Seq.App.EmailPlus/SmtpOptions.cs
+++ b/src/Seq.App.EmailPlus/SmtpOptions.cs
@@ -33,13 +33,15 @@ IEnumerable<string> GetServerList(string hostName)
             return new List<string>();
         }
 
-        public static SecureSocketOptions GetSocketOptions(bool? enableSsl, bool? useTlsWhenAvailable)
+        public static SecureSocketOptions GetSocketOptions(int port, bool? enableSsl, bool? useTlsWhenAvailable)
         {
             if (enableSsl == null) return SecureSocketOptions.Auto;
             switch (enableSsl)
             {
-                case true:
+                case true when port == 465:
                     return SecureSocketOptions.SslOnConnect;
+                case true:
+                    return SecureSocketOptions.StartTls;
                 case false when useTlsWhenAvailable != null && !(bool) useTlsWhenAvailable:
                     return SecureSocketOptions.None;
                 case false when useTlsWhenAvailable != null && (bool) useTlsWhenAvailable:
diff --git a/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs b/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
index dacb2ba..d7d47cf 100644
--- a/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
+++ b/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
@@ -3,6 +3,7 @@
 using System.Linq;
 using System.Threading.Tasks;
 using MailKit.Security;
+using MimeKit;
 using Seq.App.EmailPlus.Tests.Support;
 using Seq.Apps;
 using Seq.Apps.LogEvents;
@@ -145,10 +146,10 @@ public void SmtpOptionsCalculated()
 
             reactor.Attach(new TestAppHost());
             Assert.True(reactor.GetOptions().Host.Count() == 2);
-            Assert.True(SmtpOptions.GetSocketOptions(true, false) == SecureSocketOptions.SslOnConnect);
-            Assert.True(SmtpOptions.GetSocketOptions(false, false) == SecureSocketOptions.None);
-            Assert.True(SmtpOptions.GetSocketOptions(false, true) == SecureSocketOptions.StartTlsWhenAvailable);
-            Assert.True(SmtpOptions.GetSocketOptions(null, false) == SecureSocketOptions.Auto);
+            Assert.True(SmtpOptions.GetSocketOptions(465, true, false) == SecureSocketOptions.SslOnConnect);
+            Assert.True(SmtpOptions.GetSocketOptions(25, false, false) == SecureSocketOptions.None);
+            Assert.True(SmtpOptions.GetSocketOptions(25, false, true) == SecureSocketOptions.StartTlsWhenAvailable);
+            Assert.True(SmtpOptions.GetSocketOptions(25, null, false) == SecureSocketOptions.Auto);
         }
 
         [Fact]
@@ -233,13 +234,5 @@ public async Task ToAddressesCanBeCommaSeparated()
             Assert.Equal(3, sent.Message.To.Count);
         }
 
-        [Theory]
-        [InlineData(25, SecureSocketOptions.StartTls)]
-        [InlineData(587, SecureSocketOptions.StartTls)]
-        [InlineData(465, SecureSocketOptions.SslOnConnect)]
-        public void CorrectSecureSocketOptionsAreChosenForPort(int port, SecureSocketOptions expected)
-        {
-            Assert.Equal(expected, EmailApp.RequireSslForPort(port));
-        }
     }
 }

From b85428bd3e55d52a893c74fb5521f46b454ee847 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Sat, 28 Aug 2021 09:38:13 +1000
Subject: [PATCH 20/36] Correct port

---
 src/Seq.App.EmailPlus/EmailApp.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index ecea603..c4d34c3 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -43,7 +43,7 @@ internal EmailApp(IMailGateway mailGateway, IClock clock)
             _options = new Lazy<SmtpOptions>(() => new SmtpOptions(
                 Host,
                 DeliverUsingDns != null && (bool) DeliverUsingDns,
-                Port ?? 25,
+                port,
                 SmtpOptions.GetSocketOptions(port, EnableSsl, UseTlsWhenAvailable),
                 Username,
                 Password));

From 3a8531d2b8fef4a6599ffb25df843e323c81a1d1 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Sat, 28 Aug 2021 11:04:41 +1000
Subject: [PATCH 21/36] Reinstate and extend
 CorrectSecureSocketOptionsAreChosenForPort from #86

---
 src/Seq.App.EmailPlus/EmailApp.cs             |  2 +-
 src/Seq.App.EmailPlus/SmtpOptions.cs          |  4 +++-
 test/Seq.App.EmailPlus.Tests/EmailAppTests.cs | 21 ++++++++++++++-----
 3 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index c4d34c3..b514e4a 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -120,7 +120,7 @@ public EmailApp()
             IsOptional = true,
             DisplayName = "Require TLS",
             HelpText = "Check this box to require that the server supports SSL/TLS for sending messages. If the port used is 465," +
-                       "implicit SSL will be enabled; otherwise, the STARTTLS extension will be used. If this is disabled, Use Optional TLS If Available can be configured to allow TLS to be used when offered.")]
+                       "implicit SSL will ALWAYS be enabled; otherwise, the STARTTLS extension will be used if Require TLS is enabled. If this is disabled, Use Optional TLS If Available can be configured to allow TLS to be used when offered.")]
         public bool? EnableSsl { get; set; }
 
         [SeqAppSetting(
diff --git a/src/Seq.App.EmailPlus/SmtpOptions.cs b/src/Seq.App.EmailPlus/SmtpOptions.cs
index 82f23e9..c1d607d 100644
--- a/src/Seq.App.EmailPlus/SmtpOptions.cs
+++ b/src/Seq.App.EmailPlus/SmtpOptions.cs
@@ -38,10 +38,12 @@ public static SecureSocketOptions GetSocketOptions(int port, bool? enableSsl, bo
             if (enableSsl == null) return SecureSocketOptions.Auto;
             switch (enableSsl)
             {
-                case true when port == 465:
+                case true when port == 465: //Implicit TLS
                     return SecureSocketOptions.SslOnConnect;
                 case true:
                     return SecureSocketOptions.StartTls;
+                case false when port == 465: //Implicit TLS
+                    return SecureSocketOptions.SslOnConnect;
                 case false when useTlsWhenAvailable != null && !(bool) useTlsWhenAvailable:
                     return SecureSocketOptions.None;
                 case false when useTlsWhenAvailable != null && (bool) useTlsWhenAvailable:
diff --git a/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs b/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
index d7d47cf..7fdb85a 100644
--- a/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
+++ b/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
@@ -134,7 +134,7 @@ public async Task ToAddressesAreTemplated()
         }
 
         [Fact]
-        public void SmtpOptionsCalculated()
+        public void FallbackHostsCalculated()
         {
             var mail = new CollectingMailGateway();
             var reactor = new EmailApp(mail, new SystemClock())
@@ -146,10 +146,6 @@ public void SmtpOptionsCalculated()
 
             reactor.Attach(new TestAppHost());
             Assert.True(reactor.GetOptions().Host.Count() == 2);
-            Assert.True(SmtpOptions.GetSocketOptions(465, true, false) == SecureSocketOptions.SslOnConnect);
-            Assert.True(SmtpOptions.GetSocketOptions(25, false, false) == SecureSocketOptions.None);
-            Assert.True(SmtpOptions.GetSocketOptions(25, false, true) == SecureSocketOptions.StartTlsWhenAvailable);
-            Assert.True(SmtpOptions.GetSocketOptions(25, null, false) == SecureSocketOptions.Auto);
         }
 
         [Fact]
@@ -234,5 +230,20 @@ public async Task ToAddressesCanBeCommaSeparated()
             Assert.Equal(3, sent.Message.To.Count);
         }
 
+        [Theory]
+        [InlineData(25, null, null, SecureSocketOptions.Auto)]
+        [InlineData(25, true, false, SecureSocketOptions.StartTls)]
+        [InlineData(25, false, false, SecureSocketOptions.None)]
+        [InlineData(25, false, true, SecureSocketOptions.StartTlsWhenAvailable)]
+        [InlineData(587, true, false, SecureSocketOptions.StartTls)]
+        [InlineData(587, false, false, SecureSocketOptions.None)]
+        [InlineData(587, false, true, SecureSocketOptions.StartTlsWhenAvailable)]
+        [InlineData(465, true, false, SecureSocketOptions.SslOnConnect)]
+        [InlineData(465, false, false, SecureSocketOptions.SslOnConnect)]
+        [InlineData(465, false, true, SecureSocketOptions.SslOnConnect)]
+        public void CorrectSecureSocketOptionsAreChosenForPort(int port, bool? enableSsl, bool? optionalTls, SecureSocketOptions expected)
+        {
+            Assert.Equal(expected, SmtpOptions.GetSocketOptions(port, enableSsl, optionalTls));
+        }
     }
 }

From 38d0c5aed899cb4957e9b82ab7d77b911da66889 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Sat, 28 Aug 2021 11:26:19 +1000
Subject: [PATCH 22/36] Improve error/delivery logging for consistency

---
 src/Seq.App.EmailPlus/EmailApp.cs | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index b514e4a..502096d 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -171,7 +171,7 @@ public async Task OnAsync(Event<LogEventData> evt)
 
             if (to.Count == 0)
             {
-                Log.Error("Email 'to' address template did not evaluate to one or more recipient addresses - email cannot be sent!");
+                Log.ForContext("To", _toAddressesTemplate.Value).Error("Email 'to' address template did not evaluate to one or more recipient addresses - email cannot be sent!");
                 return;
             }
 
@@ -190,12 +190,15 @@ public async Task OnAsync(Event<LogEventData> evt)
                 toList, subject, new BodyBuilder {HtmlBody = body}.ToMessageBody());
 
             var errors = new List<Exception>();
+            var lastServer = string.Empty;
             if (_options.Value.Host != null && _options.Value.Host.Any())
             {
                 type = DeliveryType.MailHost;
                 var result = await _mailGateway.SendAsync(_options.Value, message);
                 errors = result.Errors;
                 sent = result.Success;
+                lastServer = result.LastServer;
+
                 if (!result.Success)
                 {
                     Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
@@ -215,13 +218,16 @@ public async Task OnAsync(Event<LogEventData> evt)
                 var result = await _mailGateway.SendDnsAsync(type, _options.Value, message);
                 errors = result.Errors;
                 sent = result.Success;
+                lastServer = result.LastServer;
+                type = result.Type;
 
                 if (!result.Success)
                 {
                     Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
                         .ForContext("Success", sent).ForContext("Body", body)
                         .ForContext(nameof(result.Results), result.Results, true).ForContext("Errors", errors)
-                        .ForContext(nameof(result.LastServer), result.LastServer).Error(result.LastError,
+                        .ForContext(nameof(result.Type), result.Type).ForContext(nameof(result.LastServer), result.LastServer)
+                        .Error(result.LastError,
                             "Error sending mail via DNS: {Message}, From: {From}, To: {To}, Subject: {Subject}",
                             result.LastError?.Message, From, to, subject);
                     logged = true;
@@ -231,13 +237,16 @@ public async Task OnAsync(Event<LogEventData> evt)
             if (sent)
             {
                 Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
-                    .ForContext("Success", true).ForContext("Body", body).ForContext("Errors", errors)
-                    .Information("Mail Sent, From: {From}, To: {To}, Subject: {Subject}");
+                    .ForContext("Success", true).ForContext("Body", body)
+                    .ForContext("LastServer", lastServer).ForContext("Errors", errors)
+                    .ForContext("Type", type)
+                    .Information("Mail Sent, From: {From}, To: {To}, Subject: {Subject}", From, to, subject);
             }
             else if (!logged)
                 Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
                     .ForContext("Success", true).ForContext("Body", body).ForContext("Errors", errors)
-                    .Error("Unhandled mail error, From: {From}, To: {To}, Subject: {Subject}");
+                    .ForContext("Type", type)
+                    .Error("Unhandled mail error, From: {From}, To: {To}, Subject: {Subject}", From, to, subject);
 
         }
 

From 3e2e20775ab37ddfde3324552a730da0c80dc90f Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Sat, 28 Aug 2021 11:33:19 +1000
Subject: [PATCH 23/36] Update SeqApp description

Reflects that an alternate plain text body can be set
---
 src/Seq.App.EmailPlus/EmailApp.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index bdeb624..de01db6 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -15,7 +15,7 @@ namespace Seq.App.EmailPlus
     using Template = HandlebarsTemplate<object, object>;
 
     [SeqApp("HTML Email",
-        Description = "Uses Handlebars templates to format events and notifications into HTML email.")]
+        Description = "Uses Handlebars templates to format events and notifications into HTML email, with optional alternate plain text body.")]
     public class EmailApp : SeqApp, ISubscribeToAsync<LogEventData>
     {
         readonly IMailGateway _mailGateway;

From d300106e9b472a9cd203b9807bbc58452a324819 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Tue, 31 Aug 2021 10:15:25 +1000
Subject: [PATCH 24/36] Add lastserrver to unhandled mail error

---
 src/Seq.App.EmailPlus/EmailApp.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index 502096d..2785fa6 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -245,7 +245,7 @@ public async Task OnAsync(Event<LogEventData> evt)
             else if (!logged)
                 Log.ForContext("From", From).ForContext("To", to).ForContext("Subject", subject)
                     .ForContext("Success", true).ForContext("Body", body).ForContext("Errors", errors)
-                    .ForContext("Type", type)
+                    .ForContext("Type", type).ForContext("LastServer", lastServer)
                     .Error("Unhandled mail error, From: {From}, To: {To}, Subject: {Subject}", From, to, subject);
 
         }

From 78e20444489d39f51649879b9232035c27348eae Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Tue, 31 Aug 2021 18:13:10 +1000
Subject: [PATCH 25/36] Make sure we attempt all domains

---
 src/Seq.App.EmailPlus/DirectMailGateway.cs | 46 ++++++++++++++++++----
 1 file changed, 39 insertions(+), 7 deletions(-)

diff --git a/src/Seq.App.EmailPlus/DirectMailGateway.cs b/src/Seq.App.EmailPlus/DirectMailGateway.cs
index 55f577a..9764344 100644
--- a/src/Seq.App.EmailPlus/DirectMailGateway.cs
+++ b/src/Seq.App.EmailPlus/DirectMailGateway.cs
@@ -51,6 +51,7 @@ public async Task<DnsMailResult> SendDnsAsync(DeliveryType deliveryType, SmtpOpt
             try
             {
                 var domains = GetDomains(message).ToList();
+                var successCount = 0;
 
                 foreach (var domain in domains)
                 {
@@ -59,8 +60,8 @@ public async Task<DnsMailResult> SendDnsAsync(DeliveryType deliveryType, SmtpOpt
                     var mx = await DnsClient.QueryAsync(domain, QueryType.MX);
                     var mxServers =
                         (from mxServer in mx.Answers
-                            where !string.IsNullOrEmpty(((MxRecord) mxServer).Exchange)
-                            select ((MxRecord) mxServer).Exchange).Select(dummy => (string) dummy).ToList();
+                            where !string.IsNullOrEmpty(((MxRecord)mxServer).Exchange)
+                            select ((MxRecord)mxServer).Exchange).Select(dummy => (string)dummy).ToList();
                     var mailResult = new MailResult();
                     foreach (var server in mxServers)
                     {
@@ -74,7 +75,6 @@ public async Task<DnsMailResult> SendDnsAsync(DeliveryType deliveryType, SmtpOpt
                             LastServer = server,
                             LastError = mailResult.LastError ?? lastError,
                             Type = type,
-                            Success = mailResult.Success
                         };
 
                         resultList.Add(mailResult);
@@ -84,17 +84,49 @@ public async Task<DnsMailResult> SendDnsAsync(DeliveryType deliveryType, SmtpOpt
                         type = DeliveryType.DnsFallback;
                     }
 
-                    if (mailResult.Success) continue;
-                    dnsResult.Success = false;
+                    if (mailResult.Success)
+                    {
+                        successCount++;
+                        continue;
+                    }
+
                     if (dnsResult.LastError == null)
+                    {
                         dnsResult.LastError = mxServers.Count == 0
                             ? new Exception("DNS delivery failed - no MX records detected for " + domain)
                             : new Exception("DNS delivery failed - no error detected");
-                    break;
+
+                        dnsResult.Errors.Add(dnsResult.LastError);
+                    }
                 }
 
                 if (!domains.Any())
-                    dnsResult.LastError = new Exception("DNS delivery failed - no domains parsed from To addresses");
+                {
+                    dnsResult.Success = false;
+                    dnsResult.LastError =
+                        new Exception("DNS delivery failed - no domains parsed from recipient addresses");
+                }
+
+                if (successCount < domains.Count)
+                {
+                    if (successCount == 0)
+                    {
+                        dnsResult.Success = false;
+                        dnsResult.LastError =
+                            new Exception("DNS delivery failure - no domains could be successfully delivered.");
+                    }
+                    else
+                    {
+                        dnsResult.Success = true; // A qualified success ...
+                        dnsResult.LastError =
+                            new Exception(
+                                $"DNS delivery partial failure - {domains.Count - successCount} of {successCount} domains could not be delivered.");
+                    }
+                }
+                else
+                {
+                    dnsResult.Success = true;
+                }
             }
             catch (Exception ex)
             {

From 41886beac8f49c7aed46ad06f4db597430fe0c62 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Tue, 31 Aug 2021 18:17:05 +1000
Subject: [PATCH 26/36] Catch all recipient domains in the envelope for
 processing

---
 src/Seq.App.EmailPlus/DirectMailGateway.cs | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/src/Seq.App.EmailPlus/DirectMailGateway.cs b/src/Seq.App.EmailPlus/DirectMailGateway.cs
index 9764344..bb16503 100644
--- a/src/Seq.App.EmailPlus/DirectMailGateway.cs
+++ b/src/Seq.App.EmailPlus/DirectMailGateway.cs
@@ -156,6 +156,23 @@ public static IEnumerable<string> GetDomains(MimeMessage message)
                     domains.Add(toDomain);
             }
 
+            foreach (var cc in message.Cc)
+            {
+                var ccDomain = cc.ToString().Split('@')[1];
+                if (string.IsNullOrEmpty(ccDomain)) continue;
+                if (!domains.Any(domain => domain.Equals(ccDomain, StringComparison.OrdinalIgnoreCase)))
+                    domains.Add(ccDomain);
+            }
+
+            
+            foreach (var bcc in message.Bcc)
+            {
+                var bccDomain = bcc.ToString().Split('@')[1];
+                if (string.IsNullOrEmpty(bccDomain)) continue;
+                if (!domains.Any(domain => domain.Equals(bccDomain, StringComparison.OrdinalIgnoreCase)))
+                    domains.Add(bccDomain);
+            }
+
             return domains;
         }
 

From 98e604797bc05c48fc7d200bdd4945fd2d6477ff Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Tue, 31 Aug 2021 18:30:20 +1000
Subject: [PATCH 27/36] Always catch LastError in the Errors list, always set
 Success

---
 src/Seq.App.EmailPlus/DirectMailGateway.cs | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/Seq.App.EmailPlus/DirectMailGateway.cs b/src/Seq.App.EmailPlus/DirectMailGateway.cs
index 9764344..4d983a2 100644
--- a/src/Seq.App.EmailPlus/DirectMailGateway.cs
+++ b/src/Seq.App.EmailPlus/DirectMailGateway.cs
@@ -90,14 +90,12 @@ public async Task<DnsMailResult> SendDnsAsync(DeliveryType deliveryType, SmtpOpt
                         continue;
                     }
 
-                    if (dnsResult.LastError == null)
-                    {
-                        dnsResult.LastError = mxServers.Count == 0
-                            ? new Exception("DNS delivery failed - no MX records detected for " + domain)
-                            : new Exception("DNS delivery failed - no error detected");
-
-                        dnsResult.Errors.Add(dnsResult.LastError);
-                    }
+                    if (dnsResult.LastError != null) continue;
+                    dnsResult.LastError = mxServers.Count == 0
+                        ? new Exception("DNS delivery failed - no MX records detected for " + domain)
+                        : new Exception("DNS delivery failed - no error detected");
+                    dnsResult.Success = false;
+                    dnsResult.Errors.Add(dnsResult.LastError);
                 }
 
                 if (!domains.Any())
@@ -122,6 +120,8 @@ public async Task<DnsMailResult> SendDnsAsync(DeliveryType deliveryType, SmtpOpt
                             new Exception(
                                 $"DNS delivery partial failure - {domains.Count - successCount} of {successCount} domains could not be delivered.");
                     }
+
+                    dnsResult.Errors.Add(dnsResult.LastError);
                 }
                 else
                 {

From 27006989c1f1c520fc47e4c0595415cfdf4ffdb7 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Sat, 16 Oct 2021 13:35:52 +1100
Subject: [PATCH 28/36] Use an enum and implement migration from EnableSsl per
 #89

---
 src/Seq.App.EmailPlus/DirectMailGateway.cs    |  3 +-
 src/Seq.App.EmailPlus/EmailApp.cs             | 14 +++-----
 .../Seq.App.EmailPlus.csproj                  |  7 ++--
 src/Seq.App.EmailPlus/SmtpOptions.cs          | 34 +++++++++----------
 src/Seq.App.EmailPlus/TlsOptions.cs           | 29 ++++++++++++++++
 test/Seq.App.EmailPlus.Tests/EmailAppTests.cs | 26 +++++++-------
 6 files changed, 71 insertions(+), 42 deletions(-)
 create mode 100644 src/Seq.App.EmailPlus/TlsOptions.cs

diff --git a/src/Seq.App.EmailPlus/DirectMailGateway.cs b/src/Seq.App.EmailPlus/DirectMailGateway.cs
index 4d983a2..7fd6dec 100644
--- a/src/Seq.App.EmailPlus/DirectMailGateway.cs
+++ b/src/Seq.App.EmailPlus/DirectMailGateway.cs
@@ -5,6 +5,7 @@
 using DnsClient;
 using DnsClient.Protocol;
 using MailKit.Net.Smtp;
+using MailKit.Security;
 using MimeKit;
 
 namespace Seq.App.EmailPlus
@@ -166,7 +167,7 @@ private static async Task<MailResult> TryDeliver(string server, SmtpOptions opti
                 return new MailResult {Success = false, LastServer = server, Type = deliveryType};
             try
             {
-                await Client.ConnectAsync(server, options.Port, options.SocketOptions);
+                await Client.ConnectAsync(server, options.Port, (SecureSocketOptions)options.SocketOptions);
                 if (options.RequiresAuthentication)
                     await Client.AuthenticateAsync(options.Username, options.Password);
 
diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index 2785fa6..5e6e76d 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -44,7 +44,7 @@ internal EmailApp(IMailGateway mailGateway, IClock clock)
                 Host,
                 DeliverUsingDns != null && (bool) DeliverUsingDns,
                 port,
-                SmtpOptions.GetSocketOptions(port, EnableSsl, UseTlsWhenAvailable),
+                SmtpOptions.GetSocketOptions(port, EnableSsl, EnableTls),
                 Username,
                 Password));
             // ReSharper restore ExpressionIsAlwaysNull ConditionIsAlwaysTrueOrFalse
@@ -116,18 +116,14 @@ public EmailApp()
                 "The port on the SMTP server machine to send mail to. Leave this blank to use the standard port (25).")]
         public int? Port { get; set; }
 
-        [SeqAppSetting(
-            IsOptional = true,
-            DisplayName = "Require TLS",
-            HelpText = "Check this box to require that the server supports SSL/TLS for sending messages. If the port used is 465," +
-                       "implicit SSL will ALWAYS be enabled; otherwise, the STARTTLS extension will be used if Require TLS is enabled. If this is disabled, Use Optional TLS If Available can be configured to allow TLS to be used when offered.")]
+        //EnableSSL has been retired but is preserved for migration purposes
         public bool? EnableSsl { get; set; }
 
         [SeqAppSetting(
             IsOptional = true,
-            DisplayName = "Use Optional TLS if available",
-            HelpText = "If Enable SSL is disabled but the host supports TLS, allow Seq to negotiate using TLS. This has no effect if Enable SSL is enabled.")]
-        public bool? UseTlsWhenAvailable { get; set; }
+            DisplayName = "Require TLS",
+            HelpText = "Check this box to require that the server supports SSL/TLS for sending messages. If the port used is 465, StartTls (implicit TLS) will ALWAYS be used.")]
+        public TlsOptions? EnableTls { get; set; }
 
         [SeqAppSetting(
             IsOptional = true,
diff --git a/src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj b/src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj
index 14bdb95..b035bb1 100644
--- a/src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj
+++ b/src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj
@@ -14,21 +14,24 @@
     <TreatWarningsAsErrors>True</TreatWarningsAsErrors>
     <TreatSpecificWarningsAsErrors />
     <PackageLicenseFile>LICENSE</PackageLicenseFile>
+    <PackageId>Seq.App.EmailPlus</PackageId>
+    <!--<CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>-->
   </PropertyGroup>
 
   <ItemGroup>
     <PackageReference Include="DnsClient" Version="1.5.0" />
-    <PackageReference Include="MailKit" Version="2.14.0" />
+    <PackageReference Include="MailKit" Version="2.15.0" />
     <PackageReference Include="Seq.Apps" Version="5.1.0" />
     <PackageReference Include="Serilog" Version="2.10.0" />
     <PackageReference Include="Handlebars.Net" Version="2.0.9" />
-    <PackageReference Include="Newtonsoft.Json" Version="12.0.1" />
+    <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
   </ItemGroup>
 
   <ItemGroup>
     <None Include="./icon.png" Pack="true" Visible="false" PackagePath="" />
     <None Include="../../LICENSE" Pack="true" PackagePath="" />
     <None Include="./obj/publish/**/*" Exclude="./obj/publish/Seq.App.EmailPlus.dll;./obj/publish/Seq.Apps.dll;./obj/publish/Serilog.dll" Pack="true" PackagePath="lib/$(TargetFramework)" />
+    <!--<None Include="$(OutDir)/**/*;" Exclude="$(OutDir)/$(MSBuildProjectName).dll;$(OutDir)/Seq.Apps.dll;$(OutDir)/Serilog.dll" Pack="true" PackagePath="lib/$(TargetFramework)" />-->
   </ItemGroup>
 
 </Project>
diff --git a/src/Seq.App.EmailPlus/SmtpOptions.cs b/src/Seq.App.EmailPlus/SmtpOptions.cs
index c1d607d..720abc8 100644
--- a/src/Seq.App.EmailPlus/SmtpOptions.cs
+++ b/src/Seq.App.EmailPlus/SmtpOptions.cs
@@ -13,9 +13,9 @@ public class SmtpOptions
         public string Username { get; set; } = string.Empty;
         public string Password { get; set; } = string.Empty;
         public bool RequiresAuthentication => !string.IsNullOrEmpty(Username) && !string.IsNullOrEmpty(Password);
-        public SecureSocketOptions SocketOptions { get; set; }
+        public TlsOptions SocketOptions { get; set; }
 
-        public SmtpOptions(string host, bool dnsDelivery, int port, SecureSocketOptions socketOptions, string username = null, string password = null)
+        public SmtpOptions(string host, bool dnsDelivery, int port, TlsOptions socketOptions, string username = null, string password = null)
         {
             Host = GetServerList(host).ToList();
             DnsDelivery = dnsDelivery;
@@ -33,24 +33,24 @@ IEnumerable<string> GetServerList(string hostName)
             return new List<string>();
         }
 
-        public static SecureSocketOptions GetSocketOptions(int port, bool? enableSsl, bool? useTlsWhenAvailable)
+        public static TlsOptions GetSocketOptions(int port, bool? enableSsl, TlsOptions? enableTls)
         {
-            if (enableSsl == null) return SecureSocketOptions.Auto;
-            switch (enableSsl)
+            if (enableSsl == null && enableTls == null) return TlsOptions.Auto;
+
+            switch (enableTls)
             {
-                case true when port == 465: //Implicit TLS
-                    return SecureSocketOptions.SslOnConnect;
-                case true:
-                    return SecureSocketOptions.StartTls;
-                case false when port == 465: //Implicit TLS
-                    return SecureSocketOptions.SslOnConnect;
-                case false when useTlsWhenAvailable != null && !(bool) useTlsWhenAvailable:
-                    return SecureSocketOptions.None;
-                case false when useTlsWhenAvailable != null && (bool) useTlsWhenAvailable:
-                    return SecureSocketOptions.StartTlsWhenAvailable;
+                case null when (bool)enableSsl && port == 465: //Implicit TLS
+                case TlsOptions.None when port == 465:
+                case TlsOptions.Auto when port == 465:
+                case TlsOptions.StartTlsWhenAvailable when port == 465:
+                    return TlsOptions.SslOnConnect;
+                case null when (bool)enableSsl:
+                    return TlsOptions.StartTls; //Explicit TLS
+                case null:
+                    return TlsOptions.Auto;
+                default:
+                    return (TlsOptions)enableTls;
             }
-
-            return SecureSocketOptions.Auto;
         }
     }
 }
diff --git a/src/Seq.App.EmailPlus/TlsOptions.cs b/src/Seq.App.EmailPlus/TlsOptions.cs
new file mode 100644
index 0000000..dc865e9
--- /dev/null
+++ b/src/Seq.App.EmailPlus/TlsOptions.cs
@@ -0,0 +1,29 @@
+using MailKit.Security;
+
+namespace Seq.App.EmailPlus
+{
+    public enum TlsOptions
+    {
+        /// <summary>
+        /// None
+        /// </summary>
+        None = SecureSocketOptions.None,
+        /// <summary>
+        /// Auto
+        /// </summary>
+        Auto = SecureSocketOptions.Auto,
+        /// <summary>
+        /// Implicit TLS
+        /// </summary>
+        SslOnConnect = SecureSocketOptions.SslOnConnect,
+        /// <summary>
+        /// Explicit TLS
+        /// </summary>
+        StartTls = SecureSocketOptions.StartTls,
+        /// <summary>
+        /// Optional TLS
+        /// </summary>
+        StartTlsWhenAvailable = SecureSocketOptions.StartTlsWhenAvailable
+
+    }
+}
diff --git a/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs b/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
index 7fdb85a..07d9b4f 100644
--- a/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
+++ b/test/Seq.App.EmailPlus.Tests/EmailAppTests.cs
@@ -231,19 +231,19 @@ public async Task ToAddressesCanBeCommaSeparated()
         }
 
         [Theory]
-        [InlineData(25, null, null, SecureSocketOptions.Auto)]
-        [InlineData(25, true, false, SecureSocketOptions.StartTls)]
-        [InlineData(25, false, false, SecureSocketOptions.None)]
-        [InlineData(25, false, true, SecureSocketOptions.StartTlsWhenAvailable)]
-        [InlineData(587, true, false, SecureSocketOptions.StartTls)]
-        [InlineData(587, false, false, SecureSocketOptions.None)]
-        [InlineData(587, false, true, SecureSocketOptions.StartTlsWhenAvailable)]
-        [InlineData(465, true, false, SecureSocketOptions.SslOnConnect)]
-        [InlineData(465, false, false, SecureSocketOptions.SslOnConnect)]
-        [InlineData(465, false, true, SecureSocketOptions.SslOnConnect)]
-        public void CorrectSecureSocketOptionsAreChosenForPort(int port, bool? enableSsl, bool? optionalTls, SecureSocketOptions expected)
-        {
-            Assert.Equal(expected, SmtpOptions.GetSocketOptions(port, enableSsl, optionalTls));
+        [InlineData(25, null, null, TlsOptions.Auto)]
+        [InlineData(25, true, null, TlsOptions.StartTls)]
+        [InlineData(25, false, TlsOptions.None, TlsOptions.None)]
+        [InlineData(25, false, TlsOptions.StartTlsWhenAvailable, TlsOptions.StartTlsWhenAvailable)]
+        [InlineData(587, true, TlsOptions.StartTls, TlsOptions.StartTls)]
+        [InlineData(587, false, TlsOptions.None, TlsOptions.None)]
+        [InlineData(587, false, TlsOptions.StartTlsWhenAvailable, TlsOptions.StartTlsWhenAvailable)]
+        [InlineData(465, true, TlsOptions.None, TlsOptions.SslOnConnect)]
+        [InlineData(465, false, TlsOptions.Auto, TlsOptions.SslOnConnect)]
+        [InlineData(465, false, TlsOptions.SslOnConnect, TlsOptions.SslOnConnect)]
+        public void CorrectSecureSocketOptionsAreChosenForPort(int port, bool? enableSsl, TlsOptions? enableTls, TlsOptions expected)
+        {
+            Assert.Equal(expected, SmtpOptions.GetSocketOptions(port, enableSsl, enableTls));
         }
     }
 }

From d8d7f06906921c0eb7415a6bcf23923077a6383a Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Sat, 16 Oct 2021 14:05:17 +1100
Subject: [PATCH 29/36] Merge #81 changes resulting from #89

---
 src/Seq.App.EmailPlus/SmtpOptions.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Seq.App.EmailPlus/SmtpOptions.cs b/src/Seq.App.EmailPlus/SmtpOptions.cs
index 29ddd7b..ec5c7ae 100644
--- a/src/Seq.App.EmailPlus/SmtpOptions.cs
+++ b/src/Seq.App.EmailPlus/SmtpOptions.cs
@@ -18,7 +18,7 @@ public class SmtpOptions
         public EmailPriority DefaultPriority { get; set; }
         public TlsOptions SocketOptions { get; set; }
 
-        public SmtpOptions(string host, bool dnsDelivery, int port, TlsOptions socketOptions, string username = null, string password = null)
+        public SmtpOptions(string host, bool dnsDelivery, int port, string priority, string defaultPriority, TlsOptions socketOptions, string username = null, string password = null)
         {
             Host = GetServerList(host).ToList();
             DnsDelivery = dnsDelivery;

From a1a600f5ce730508addaf5ce5afafa2afe52123c Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Mon, 1 Nov 2021 14:13:45 +1100
Subject: [PATCH 30/36] Merge changes from #93

---
 src/Seq.App.EmailPlus/EmailApp.cs | 34 ++++++++++++-------------------
 1 file changed, 13 insertions(+), 21 deletions(-)

diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index f5c9c95..b589751 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -120,15 +120,17 @@ public EmailApp()
         
         protected override void OnAttached()
         {
+                        if (string.IsNullOrEmpty(Host) && (DeliverUsingDns == null || !(bool) DeliverUsingDns))
+                throw new Exception("There are no delivery methods selected - you must specify at least one SMTP Mail Host, or enable Deliver Using DNS");
+
             var port = Port ?? DefaultPort;
             _options = _options = new SmtpOptions(
                 Host,
+                DeliverUsingDns != null && (bool)DeliverUsingDns,
                 port,
-                EnableSsl ?? false
-                    ? RequireSslForPort(port)
-                    : SecureSocketOptions.StartTlsWhenAvailable,
+                SmtpOptions.GetSocketOptions(port, EnableSsl, EnableTls),
                 Username,
-                Password);
+                Password);;
 
             _subjectTemplate = Handlebars.Compile(string.IsNullOrEmpty(SubjectTemplate) 
                 ? DefaultSubjectTemplate 
@@ -139,23 +141,18 @@ protected override void OnAttached()
             _toAddressesTemplate = string.IsNullOrEmpty(To) ? (_, __) => To : Handlebars.Compile(To);
         }
 
-        protected override void OnAttached()
-        {
-            if (string.IsNullOrEmpty(Host) && (DeliverUsingDns == null || !(bool) DeliverUsingDns))
-                throw new Exception("There are no delivery methods selected - you must specify at least one SMTP Mail Host, or enable Deliver Using DNS");
-        }
 
         public async Task OnAsync(Event<LogEventData> evt)
         {
             if (ShouldSuppress(evt)) return;
 
-            var to = FormatTemplate(_toAddressesTemplate.Value, evt, base.Host)
+            var to = FormatTemplate(_toAddressesTemplate, evt, base.Host)
                 .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
                 .Select(t => t.Trim()).ToList();
 
             if (to.Count == 0)
             {
-                Log.ForContext("To", _toAddressesTemplate.Value).Error("Email 'to' address template did not evaluate to one or more recipient addresses - email cannot be sent!");
+                Log.ForContext("To", _toAddressesTemplate).Error("Email 'to' address template did not evaluate to one or more recipient addresses - email cannot be sent!");
                 return;
             }
 
@@ -175,10 +172,10 @@ public async Task OnAsync(Event<LogEventData> evt)
 
             var errors = new List<Exception>();
             var lastServer = string.Empty;
-            if (_options.Value.Host != null && _options.Value.Host.Any())
+            if (_options.Host != null && _options.Host.Any())
             {
                 type = DeliveryType.MailHost;
-                var result = await _mailGateway.SendAsync(_options.Value, message);
+                var result = await _mailGateway.SendAsync(_options, message);
                 errors = result.Errors;
                 sent = result.Success;
                 lastServer = result.LastServer;
@@ -196,10 +193,10 @@ public async Task OnAsync(Event<LogEventData> evt)
                 }
             }
 
-            if (!sent && _options.Value.DnsDelivery)
+            if (!sent && _options.DnsDelivery)
             {
                 type = type == DeliveryType.None ? DeliveryType.Dns : DeliveryType.HostDnsFallback;
-                var result = await _mailGateway.SendDnsAsync(type, _options.Value, message);
+                var result = await _mailGateway.SendDnsAsync(type, _options, message);
                 errors = result.Errors;
                 sent = result.Success;
                 lastServer = result.LastServer;
@@ -263,11 +260,6 @@ bool ShouldSuppress(Event<LogEventData> evt)
             return true;
         }
 
-        internal static SecureSocketOptions RequireSslForPort(int port)
-        {
-            return (port == DefaultSslPort ? SecureSocketOptions.SslOnConnect : SecureSocketOptions.StartTls);
-        }
-        
         internal static string FormatTemplate(Template template, Event<LogEventData> evt, Host host)
         {
             var properties =
@@ -322,7 +314,7 @@ static object ToDynamic(object o)
 
         public SmtpOptions GetOptions()
         {
-            return _options.Value;
+            return _options;
         }
     }
 }

From 500439c376409aa4ab8c1b41a214581be2a6767a Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Mon, 1 Nov 2021 14:45:31 +1100
Subject: [PATCH 31/36] Merge changes resulting from #93, and merge to
 DeliveryEnhancements branch

---
 src/Seq.App.EmailPlus/EmailApp.cs | 67 +++++++++++++++++--------------
 1 file changed, 36 insertions(+), 31 deletions(-)

diff --git a/src/Seq.App.EmailPlus/EmailApp.cs b/src/Seq.App.EmailPlus/EmailApp.cs
index 1400ff6..b94d46c 100644
--- a/src/Seq.App.EmailPlus/EmailApp.cs
+++ b/src/Seq.App.EmailPlus/EmailApp.cs
@@ -163,61 +163,71 @@ public EmailApp()
         
         protected override void OnAttached()
         {
+            if (string.IsNullOrEmpty(Host) && (DeliverUsingDns == null || !(bool) DeliverUsingDns))
+                throw new Exception("There are no delivery methods selected - you must specify at least one SMTP Mail Host, or enable Deliver Using DNS");
+
             var port = Port ?? DefaultPort;
             _options = _options = new SmtpOptions(
                 Host,
+                DeliverUsingDns != null && (bool)DeliverUsingDns,
                 port,
-                EnableSsl ?? false
-                    ? RequireSslForPort(port)
-                    : SecureSocketOptions.StartTlsWhenAvailable,
+                Priority,
+                DefaultPriority,
+                SmtpOptions.GetSocketOptions(port, EnableSsl, EnableTls),
                 Username,
                 Password);
 
             _subjectTemplate = Handlebars.Compile(string.IsNullOrEmpty(SubjectTemplate) 
                 ? DefaultSubjectTemplate 
                 : SubjectTemplate);
+
             _bodyTemplate = Handlebars.Compile(string.IsNullOrEmpty(BodyTemplate) 
                 ? Resources.DefaultBodyTemplate 
                 : BodyTemplate);
+
+            _plainTextTemplate = Handlebars.Compile(string.IsNullOrEmpty(PlainTextTemplate)
+                ? Resources.DefaultBodyTemplate
+                : PlainTextTemplate);
+            
             _toAddressesTemplate = string.IsNullOrEmpty(To) ? (_, __) => To : Handlebars.Compile(To);
-        }
 
-        protected override void OnAttached()
-        {
-            if (string.IsNullOrEmpty(Host) && (DeliverUsingDns == null || !(bool) DeliverUsingDns))
-                throw new Exception("There are no delivery methods selected - you must specify at least one SMTP Mail Host, or enable Deliver Using DNS");
+            _replyToAddressesTemplate = string.IsNullOrEmpty(ReplyTo) ? (_, __) => ReplyTo : Handlebars.Compile(ReplyTo);
+
+            _ccAddressesTemplate = string.IsNullOrEmpty(Cc) ? (_, __) => Cc : Handlebars.Compile(Cc);
+
+            _bccAddressesTemplate = string.IsNullOrEmpty(Bcc) ? (_, __) => Bcc : Handlebars.Compile(Bcc);
         }
 
         public async Task OnAsync(Event<LogEventData> evt)
         {
             if (ShouldSuppress(evt)) return;
 
-            var to = FormatTemplate(_toAddressesTemplate.Value, evt, base.Host)
+            var to = FormatTemplate(_toAddressesTemplate, evt, base.Host)
                 .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
                 .Select(t => t.Trim()).ToList();
 
             if (to.Count == 0)
             {
-                Log.ForContext("To", _toAddressesTemplate.Value).Error("Email 'to' address template did not evaluate to one or more recipient addresses - email cannot be sent!");
+                Log.ForContext("To", _toAddressesTemplate).Error("Email 'to' address template did not evaluate to one or more recipient addresses - email cannot be sent!");
                 return;
             }
 
-            var replyTo = string.IsNullOrEmpty(ReplyTo) ? new List<string>() : FormatTemplate(_replyToAddressesTemplate.Value, evt, base.Host)
+            var replyTo = string.IsNullOrEmpty(ReplyTo) ? new List<string>() : FormatTemplate(_replyToAddressesTemplate, evt, base.Host)
                 .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
                 .Select(t => t.Trim()).ToList();
 
-            var cc = string.IsNullOrEmpty(Cc) ? new List<string>() : FormatTemplate(_ccAddressesTemplate.Value, evt, base.Host)
+            var cc = string.IsNullOrEmpty(Cc) ? new List<string>() : FormatTemplate(_ccAddressesTemplate, evt, base.Host)
                 .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
                 .Select(t => t.Trim()).ToList();
 
-            var bcc = string.IsNullOrEmpty(Bcc) ? new List<string>() : FormatTemplate(_bccAddressesTemplate.Value, evt, base.Host)
+            var bcc = string.IsNullOrEmpty(Bcc) ? new List<string>() : FormatTemplate(_bccAddressesTemplate, evt, base.Host)
                 .Split(new[] {','}, StringSplitOptions.RemoveEmptyEntries)
                 .Select(t => t.Trim()).ToList();
 
 
-            var body = FormatTemplate(_bodyTemplate.Value, evt, base.Host);
-            var textBody = FormatTemplate(_plainTextTemplate.Value, evt, base.Host);
-            var subject = FormatTemplate(_subjectTemplate.Value, evt, base.Host).Trim().Replace("\r", "")
+            var body = FormatTemplate(_bodyTemplate, evt, base.Host);
+            var textBody = FormatTemplate(_plainTextTemplate, evt, base.Host);
+            var subject = FormatTemplate(_subjectTemplate, evt, base.Host).Trim().Replace("\r", "")
                 .Replace("\n", "");
             if (subject.Length > MaxSubjectLength)
                 subject = subject.Substring(0, MaxSubjectLength);
@@ -245,21 +255,21 @@ public async Task OnAsync(Event<LogEventData> evt)
                 message.Bcc.AddRange(bccList);
 
             var priority = EmailPriority.Normal;
-            switch (_options.Value.Priority)
+            switch (_options.Priority)
             {
                 case EmailPriority.UseMapping:
-                    if (!string.IsNullOrEmpty(PriorityProperty) && _options.Value.PriorityMapping.Count > 0 &&
+                    if (!string.IsNullOrEmpty(PriorityProperty) && _options.PriorityMapping.Count > 0 &&
                         TryGetPropertyValueCI(evt.Data.Properties, PriorityProperty, out var priorityProperty) &&
                         priorityProperty is string priorityValue &&
-                        _options.Value.PriorityMapping.TryGetValue(priorityValue, out var matchedPriority))
+                        _options.PriorityMapping.TryGetValue(priorityValue, out var matchedPriority))
                         priority = matchedPriority;
                     else
-                        priority = _options.Value.DefaultPriority;
+                        priority = _options.DefaultPriority;
                     break;
                 case EmailPriority.Low:
                 case EmailPriority.Normal:
                 case EmailPriority.High:
-                    priority = _options.Value.Priority;
+                    priority = _options.Priority;
                     break;
                 default:
                     priority = EmailPriority.Normal;
@@ -269,10 +279,10 @@ priorityProperty is string priorityValue &&
             message.Priority = (MessagePriority) priority;
             var errors = new List<Exception>();
             var lastServer = string.Empty;
-            if (_options.Value.Host != null && _options.Value.Host.Any())
+            if (_options.Host != null && _options.Host.Any())
             {
                 type = DeliveryType.MailHost;
-                var result = await _mailGateway.SendAsync(_options.Value, message);
+                var result = await _mailGateway.SendAsync(_options, message);
                 errors = result.Errors;
                 sent = result.Success;
                 lastServer = result.LastServer;
@@ -292,10 +302,10 @@ priorityProperty is string priorityValue &&
                 }
             }
 
-            if (!sent && _options.Value.DnsDelivery)
+            if (!sent && _options.DnsDelivery)
             {
                 type = type == DeliveryType.None ? DeliveryType.Dns : DeliveryType.HostDnsFallback;
-                var result = await _mailGateway.SendDnsAsync(type, _options.Value, message);
+                var result = await _mailGateway.SendDnsAsync(type, _options, message);
                 errors = result.Errors;
                 sent = result.Success;
                 lastServer = result.LastServer;
@@ -362,11 +372,6 @@ bool ShouldSuppress(Event<LogEventData> evt)
             // Suppressed
             return true;
         }
-
-        internal static SecureSocketOptions RequireSslForPort(int port)
-        {
-            return (port == DefaultSslPort ? SecureSocketOptions.SslOnConnect : SecureSocketOptions.StartTls);
-        }
         
         internal static string FormatTemplate(Template template, Event<LogEventData> evt, Host host)
         {
@@ -436,7 +441,7 @@ static bool TryGetPropertyValueCI(IReadOnlyDictionary<string, object> properties
 		
         public SmtpOptions GetOptions()
         {
-            return _options.Value;
+            return _options;
         }
     }
 }

From 0e26adb7776ecf63d2309712b709ffea62748a4c Mon Sep 17 00:00:00 2001
From: MattMofDoom <matt.marlor@outlook.com>
Date: Tue, 1 Feb 2022 00:33:09 +1100
Subject: [PATCH 32/36] Update dependencies

---
 src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj            | 8 ++++----
 .../Seq.App.EmailPlus.Tests.csproj                        | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj b/src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj
index b035bb1..e6b9826 100644
--- a/src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj
+++ b/src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj
@@ -19,11 +19,11 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="DnsClient" Version="1.5.0" />
-    <PackageReference Include="MailKit" Version="2.15.0" />
-    <PackageReference Include="Seq.Apps" Version="5.1.0" />
+    <PackageReference Include="DnsClient" Version="1.6.0" />
+    <PackageReference Include="MailKit" Version="3.1.1" />
+    <PackageReference Include="Seq.Apps" Version="2021.4.0" />
     <PackageReference Include="Serilog" Version="2.10.0" />
-    <PackageReference Include="Handlebars.Net" Version="2.0.9" />
+    <PackageReference Include="Handlebars.Net" Version="2.1.0" />
     <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
   </ItemGroup>
 
diff --git a/test/Seq.App.EmailPlus.Tests/Seq.App.EmailPlus.Tests.csproj b/test/Seq.App.EmailPlus.Tests/Seq.App.EmailPlus.Tests.csproj
index d202f51..a9f0404 100644
--- a/test/Seq.App.EmailPlus.Tests/Seq.App.EmailPlus.Tests.csproj
+++ b/test/Seq.App.EmailPlus.Tests/Seq.App.EmailPlus.Tests.csproj
@@ -7,7 +7,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.10.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.0.0" />
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3">
       <PrivateAssets>all</PrivateAssets>

From 37a89b86069b81538958c61b9c1a3f0dc1977a72 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Thu, 19 May 2022 10:27:23 +1000
Subject: [PATCH 33/36] Minimal reversion of changes preventing Visual Studio
 earlier than 2022

---
 global.json => bak/global.json                              | 0
 test/Seq.App.EmailPlus.Tests/Seq.App.EmailPlus.Tests.csproj | 2 +-
 2 files changed, 1 insertion(+), 1 deletion(-)
 rename global.json => bak/global.json (100%)

diff --git a/global.json b/bak/global.json
similarity index 100%
rename from global.json
rename to bak/global.json
diff --git a/test/Seq.App.EmailPlus.Tests/Seq.App.EmailPlus.Tests.csproj b/test/Seq.App.EmailPlus.Tests/Seq.App.EmailPlus.Tests.csproj
index 870f6e2..20cac74 100644
--- a/test/Seq.App.EmailPlus.Tests/Seq.App.EmailPlus.Tests.csproj
+++ b/test/Seq.App.EmailPlus.Tests/Seq.App.EmailPlus.Tests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>netstandard2.0</TargetFramework>
     <IsPackable>false</IsPackable>
   </PropertyGroup>
 

From b2d43e465aae0f83c895d4f82068c0752413fa44 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Thu, 19 May 2022 10:43:13 +1000
Subject: [PATCH 34/36] Update dependencies

---
 src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj              | 4 ++--
 test/Seq.App.EmailPlus.Tests/Seq.App.EmailPlus.Tests.csproj | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj b/src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj
index 3c4b20c..99f6a41 100644
--- a/src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj
+++ b/src/Seq.App.EmailPlus/Seq.App.EmailPlus.csproj
@@ -20,9 +20,9 @@
 
   <ItemGroup>
     <PackageReference Include="DnsClient" Version="1.6.0" />
-    <PackageReference Include="MailKit" Version="3.1.1" />
+    <PackageReference Include="MailKit" Version="3.2.0" />
     <PackageReference Include="Seq.Apps" Version="2021.4.0" />
-    <PackageReference Include="Serilog" Version="2.10.0" />
+    <PackageReference Include="Serilog" Version="2.11.0" />
     <PackageReference Include="Handlebars.Net" Version="2.1.2" />
     <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
   </ItemGroup>
diff --git a/test/Seq.App.EmailPlus.Tests/Seq.App.EmailPlus.Tests.csproj b/test/Seq.App.EmailPlus.Tests/Seq.App.EmailPlus.Tests.csproj
index 20cac74..43525b5 100644
--- a/test/Seq.App.EmailPlus.Tests/Seq.App.EmailPlus.Tests.csproj
+++ b/test/Seq.App.EmailPlus.Tests/Seq.App.EmailPlus.Tests.csproj
@@ -6,9 +6,9 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.0.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.2.0" />
     <PackageReference Include="xunit" Version="2.4.1" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3">
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>

From 11603263b31af1650b5cac4ba62eaf90baf450b7 Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Thu, 19 May 2022 10:59:56 +1000
Subject: [PATCH 35/36] Revert to earlier build script to address error

---
 Build.ps1 | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/Build.ps1 b/Build.ps1
index 5f4a1e6..8bf0f0d 100644
--- a/Build.ps1
+++ b/Build.ps1
@@ -10,7 +10,7 @@ if(Test-Path .\artifacts) {
 }
 
 & dotnet restore --no-cache
-if($LASTEXITCODE -ne 0) { throw "Build failed with exit code $LASTEXITCODE" }    
+if($LASTEXITCODE -ne 0) { exit 1 }    
 
 $branch = @{ $true = $env:APPVEYOR_REPO_BRANCH; $false = $(git symbolic-ref --short -q HEAD) }[$env:APPVEYOR_REPO_BRANCH -ne $NULL];
 $revision = @{ $true = "{0:00000}" -f [convert]::ToInt32("0" + $env:APPVEYOR_BUILD_NUMBER, 10); $false = "local" }[$env:APPVEYOR_BUILD_NUMBER -ne $NULL];
@@ -30,7 +30,7 @@ foreach ($src in ls src/*) {
         & dotnet publish -c Release -o ./obj/publish
         & dotnet pack -c Release -o ..\..\artifacts --no-build
     }
-    if($LASTEXITCODE -ne 0) { throw "Build failed with exit code $LASTEXITCODE" }    
+    if($LASTEXITCODE -ne 0) { exit 1 }    
 
     Pop-Location
 }
@@ -41,9 +41,9 @@ foreach ($test in ls test/*.Tests) {
     echo "build: Testing project in $test"
 
     & dotnet test -c Release
-    if($LASTEXITCODE -ne 0) { throw "Build failed with exit code $LASTEXITCODE" }
+    if($LASTEXITCODE -ne 0) { exit 3 }
 
     Pop-Location
 }
 
-Pop-Location
+Pop-Location
\ No newline at end of file

From 012cc976ddc744af4b21714ef5426b1dcb55294b Mon Sep 17 00:00:00 2001
From: MattMofDoom <30714560+MattMofDoom@users.noreply.github.com>
Date: Thu, 19 May 2022 11:02:18 +1000
Subject: [PATCH 36/36] Move build back to VS 2019 to address error

---
 appveyor.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/appveyor.yml b/appveyor.yml
index 137223f..98c8907 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,6 +1,6 @@
 version: '{build}'
 skip_tags: true
-image: Visual Studio 2022
+image: Visual Studio 2019
 install:
 build_script:
   - pwsh: ./Build.ps1