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fix: route inbound email by envelope recipient #48

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fix: route inbound email by envelope recipient #48

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46 changes: 36 additions & 10 deletions workers/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -329,6 +329,25 @@ app.get("/api/v1/mailboxes/:mailboxId/emails/:emailId/attachments/:attachmentId"

const MAX_EMAIL_SIZE = 25 * 1024 * 1024;

type IncomingEmailMessage = {
raw: ReadableStream;
rawSize: number;
to?: string;
};

function normalizeAddress(address: string | null | undefined) {
const normalized = address?.trim().toLowerCase();
return normalized || undefined;
}

function parsedAddressList(
addresses: Array<{ address?: string | null }> | undefined,
) {
return (addresses
?.map((entry) => normalizeAddress(entry.address))
.filter((address): address is string => Boolean(address))) ?? [];
}

async function streamToArrayBuffer(stream: ReadableStream, streamSize: number) {
if (streamSize > MAX_EMAIL_SIZE) throw new Error(`Email too large: ${streamSize} bytes exceeds ${MAX_EMAIL_SIZE} byte limit`);
if (streamSize <= 0) throw new Error(`Invalid stream size: ${streamSize}`);
Expand All @@ -345,22 +364,29 @@ async function streamToArrayBuffer(stream: ReadableStream, streamSize: number) {
return result;
}

async function receiveEmail(event: { raw: ReadableStream; rawSize: number }, env: Env, ctx: ExecutionContext) {
async function receiveEmail(event: IncomingEmailMessage, env: Env, ctx: ExecutionContext) {
const rawEmail = await streamToArrayBuffer(event.raw, event.rawSize);
const parsedEmail = await new PostalMime().parse(rawEmail);

if (!parsedEmail.to?.length || !parsedEmail.to[0].address) throw new Error("received email with empty to");
const envelopeRecipient = normalizeAddress(event.to);
const allRecipients = parsedAddressList(parsedEmail.to);
if (!envelopeRecipient && allRecipients.length === 0) throw new Error("received email with empty to");

const allowedAddresses = ((env.EMAIL_ADDRESSES ?? []) as string[]).map((a) => a.toLowerCase());
const allRecipients = parsedEmail.to.map((t) => t.address?.toLowerCase()).filter(Boolean) as string[];
const ccRecipients = (parsedEmail.cc || []).map((e) => e.address?.toLowerCase()).filter(Boolean) as string[];
const bccRecipients = (parsedEmail.bcc || []).map((e) => e.address?.toLowerCase()).filter(Boolean) as string[];
const allowedAddresses = ((env.EMAIL_ADDRESSES ?? []) as string[])
.map((a) => normalizeAddress(a))
.filter(Boolean) as string[];
const ccRecipients = parsedAddressList(parsedEmail.cc);
const bccRecipients = parsedAddressList(parsedEmail.bcc);

let mailboxId: string | undefined;
if (allowedAddresses.length > 0) {
mailboxId = allRecipients.find((addr) => allowedAddresses.includes(addr));
if (!mailboxId) { console.log(`Ignoring email: no recipient matches EMAIL_ADDRESSES.`); return; }
} else { mailboxId = allRecipients[0]; }
const routingRecipients = envelopeRecipient ? [envelopeRecipient] : allRecipients;
mailboxId = routingRecipients.find((addr) => allowedAddresses.includes(addr));
if (!mailboxId) {
console.log(`Ignoring email for ${envelopeRecipient ?? allRecipients.join(", ")}: recipient is not configured in EMAIL_ADDRESSES.`);
return;
}
} else { mailboxId = envelopeRecipient ?? allRecipients[0]; }
if (!mailboxId) throw new Error("received email with no valid recipient address");

const messageId = crypto.randomUUID();
Expand Down Expand Up @@ -394,7 +420,7 @@ async function receiveEmail(event: { raw: ReadableStream; rawSize: number }, env

await stub.createEmail(Folders.INBOX, {
id: messageId, subject: parsedEmail.subject || "",
sender: (parsedEmail.from?.address || "").toLowerCase(), recipient: allRecipients.join(", "),
sender: (parsedEmail.from?.address || "").toLowerCase(), recipient: (allRecipients.length > 0 ? allRecipients : [mailboxId]).join(", "),
cc: ccRecipients.join(", ") || null, bcc: bccRecipients.join(", ") || null,
date: new Date().toISOString(), // uses receive time, not the email's Date header
body: parsedEmail.html || parsedEmail.text || "",
Expand Down