diff --git a/src/main/java/clap/server/adapter/outbound/jwt/access/AccessTokenProvider.java b/src/main/java/clap/server/adapter/outbound/jwt/access/AccessTokenProvider.java
index 918555b3..371e8631 100644
--- a/src/main/java/clap/server/adapter/outbound/jwt/access/AccessTokenProvider.java
+++ b/src/main/java/clap/server/adapter/outbound/jwt/access/AccessTokenProvider.java
@@ -71,7 +71,7 @@ public boolean isTokenExpired(String token) {
             return claims.getExpiration().before(new Date());
         } catch (Exception e) {
             log.error("Token is expired: {}", e.getMessage());
-            throw new JwtException(AuthErrorCode.EMPTY_ACCESS_KEY);
+            throw new JwtException(AuthErrorCode.EXPIRED_TOKEN);
         }
     }
 
diff --git a/src/main/java/clap/server/adapter/outbound/jwt/access/temporary/TemporaryTokenProvider.java b/src/main/java/clap/server/adapter/outbound/jwt/access/temporary/TemporaryTokenProvider.java
index 6dd921ae..fe0e18db 100644
--- a/src/main/java/clap/server/adapter/outbound/jwt/access/temporary/TemporaryTokenProvider.java
+++ b/src/main/java/clap/server/adapter/outbound/jwt/access/temporary/TemporaryTokenProvider.java
@@ -71,7 +71,7 @@ public boolean isTokenExpired(String token) {
             return claims.getExpiration().before(new Date());
         } catch (Exception e) {
             log.error("Token is expired: {}", e.getMessage());
-            throw new JwtException(AuthErrorCode.EMPTY_ACCESS_KEY);
+            throw new JwtException(AuthErrorCode.EXPIRED_TOKEN);
         }
     }
 
diff --git a/src/main/java/clap/server/adapter/outbound/jwt/refresh/RefreshTokenProvider.java b/src/main/java/clap/server/adapter/outbound/jwt/refresh/RefreshTokenProvider.java
index f434181b..1326f037 100644
--- a/src/main/java/clap/server/adapter/outbound/jwt/refresh/RefreshTokenProvider.java
+++ b/src/main/java/clap/server/adapter/outbound/jwt/refresh/RefreshTokenProvider.java
@@ -68,7 +68,7 @@ public boolean isTokenExpired(String token) {
             return claims.getExpiration().before(new Date());
         } catch (Exception e) {
             log.error("Token is expired: {}", e.getMessage());
-            throw new JwtException(AuthErrorCode.EMPTY_ACCESS_KEY);
+            throw new JwtException(AuthErrorCode.EXPIRED_TOKEN);
         }
     }
 
diff --git a/src/main/java/clap/server/application/service/admin/SendInvitationEmailService.java b/src/main/java/clap/server/application/service/admin/SendInvitationEmailService.java
new file mode 100644
index 00000000..f7795289
--- /dev/null
+++ b/src/main/java/clap/server/application/service/admin/SendInvitationEmailService.java
@@ -0,0 +1,29 @@
+package clap.server.application.service.admin;
+
+import clap.server.application.port.outbound.email.SendEmailPort;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.stereotype.Service;
+
+import java.util.concurrent.CompletableFuture;
+@Slf4j
+@Service
+@RequiredArgsConstructor
+public class SendInvitationEmailService {
+    private final SendEmailPort sendEmailPort;
+
+    @Async("emailExecutor")
+    public void sendInvitationEmail(String memberEmail, String receiverName, String initialPassword, String userNickname) {
+        CompletableFuture.runAsync(() -> {
+            try {
+                sendEmailPort.sendInvitationEmail(memberEmail, receiverName, initialPassword, userNickname);
+            } catch (Exception e) {
+                log.error("Failed to send new password email to: {}", memberEmail, e);
+            }
+        }).exceptionally(ex -> {
+            log.error("Unexpected error occurred while sending new password email", ex);
+            return null;
+        });
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/clap/server/application/service/admin/SendInvitationService.java b/src/main/java/clap/server/application/service/admin/SendInvitationService.java
index 7981a6e1..f350726c 100644
--- a/src/main/java/clap/server/application/service/admin/SendInvitationService.java
+++ b/src/main/java/clap/server/application/service/admin/SendInvitationService.java
@@ -4,7 +4,6 @@
 import clap.server.application.port.inbound.admin.SendInvitationUsecase;
 import clap.server.application.port.outbound.member.CommandMemberPort;
 import clap.server.application.port.outbound.member.LoadMemberPort;
-import clap.server.application.port.outbound.email.SendEmailPort;
 import clap.server.common.annotation.architecture.ApplicationService;
 import clap.server.common.utils.InitialPasswordGenerator;
 import clap.server.domain.model.member.Member;
@@ -19,7 +18,7 @@
 public class SendInvitationService implements SendInvitationUsecase {
     private final LoadMemberPort loadMemberPort;
     private final CommandMemberPort commandMemberPort;
-    private final SendEmailPort sendEmailPort;
+    private final SendInvitationEmailService sendInvitationEmailService;
     private final InitialPasswordGenerator passwordGenerator;
     private final PasswordEncoder passwordEncoder;
 
@@ -37,7 +36,7 @@ public void sendInvitation(SendInvitationRequest request) {
 
         member.changeToApproveRequested();
 
-        sendEmailPort.sendInvitationEmail(
+        sendInvitationEmailService.sendInvitationEmail(
                 member.getMemberInfo().getEmail(),
                 member.getMemberInfo().getName(),
                 initialPassword,
diff --git a/src/main/java/clap/server/application/service/member/ResetPasswordService.java b/src/main/java/clap/server/application/service/member/ResetPasswordService.java
index 59ce3e39..488def12 100644
--- a/src/main/java/clap/server/application/service/member/ResetPasswordService.java
+++ b/src/main/java/clap/server/application/service/member/ResetPasswordService.java
@@ -5,7 +5,6 @@
 import clap.server.application.port.inbound.member.ResetInitialPasswordUsecase;
 import clap.server.application.port.inbound.member.ResetPasswordUsecase;
 import clap.server.application.port.inbound.member.SendNewPasswordUsecase;
-import clap.server.application.port.outbound.email.SendEmailPort;
 import clap.server.application.port.outbound.member.CommandMemberPort;
 import clap.server.application.port.outbound.member.LoadMemberPort;
 import clap.server.common.annotation.architecture.ApplicationService;
@@ -28,7 +27,7 @@ class ResetPasswordService implements ResetPasswordUsecase, ResetInitialPassword
     private final CommandMemberPort commandMemberPort;
     private final LoadMemberPort loadMemberPort;
     private final InitialPasswordGenerator initialPasswordGenerator;
-    private final SendEmailPort sendEmailPort;
+    private final SendPasswordEmailService sendPasswordEmailService;
 
     @Override
     public void resetPassword(Long memberId, String inputPassword) {
@@ -52,7 +51,7 @@ public void sendInitialPassword(SendInitialPasswordRequest request) {
                         () -> new ApplicationException(MemberErrorCode.MEMBER_NOT_FOUND));
 
         String newPassword = initialPasswordGenerator.generateRandomPassword();
-        sendEmailPort.sendNewPasswordEmail(request.email(), request.name(), newPassword);
+        sendPasswordEmailService.sendNewPasswordEmail(request.email(), request.name(), newPassword);
         String encodedPassword = passwordEncoder.encode(newPassword);
         member.resetPassword(encodedPassword);
         commandMemberPort.save(member);
diff --git a/src/main/java/clap/server/application/service/member/SendPasswordEmailService.java b/src/main/java/clap/server/application/service/member/SendPasswordEmailService.java
new file mode 100644
index 00000000..6e122826
--- /dev/null
+++ b/src/main/java/clap/server/application/service/member/SendPasswordEmailService.java
@@ -0,0 +1,30 @@
+package clap.server.application.service.member;
+
+import clap.server.application.port.outbound.email.SendEmailPort;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.stereotype.Service;
+
+import java.util.concurrent.CompletableFuture;
+
+@Slf4j
+@Service
+@RequiredArgsConstructor
+public class SendPasswordEmailService {
+    private final SendEmailPort sendEmailPort;
+
+    @Async("emailExecutor")
+    public void sendNewPasswordEmail(String email, String name, String newPassword) {
+        CompletableFuture.runAsync(() -> {
+            try {
+                sendEmailPort.sendNewPasswordEmail(email, name, newPassword);
+            } catch (Exception e) {
+                log.error("Failed to send new password email to: {}", email, e);
+            }
+        }).exceptionally(ex -> {
+            log.error("Unexpected error occurred while sending new password email", ex);
+            return null;
+        });
+    }
+}
diff --git a/src/main/java/clap/server/domain/model/task/Task.java b/src/main/java/clap/server/domain/model/task/Task.java
index bab637dc..4af89644 100644
--- a/src/main/java/clap/server/domain/model/task/Task.java
+++ b/src/main/java/clap/server/domain/model/task/Task.java
@@ -98,7 +98,7 @@ public void approveTask(Member reviewer, Member processor, LocalDateTime dueDate
     }
 
     private static String toTaskCode(Category category) {
-        return category.getMainCategory().getCode() + LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyMMddHHmm"));
+        return category.getMainCategory().getCode() + category.getCode() + LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyMMddHHmm"));
     }
 
     public void updateProcessorOrder(long newProcessorOrder) {