fix: SendEmail - fixed issue where standard MimeMessage-Headers were duplicated instead of overwritten when set in the request

Author: jhartmann123

src/Directory.Build.props

@@ -1,6 +1,6 @@
 <Project>
   <PropertyGroup>
-    <Version>9.5.3</Version>
+    <Version>9.5.4</Version>
     <TargetFramework>net8.0</TargetFramework>
   </PropertyGroup>
 

src/Email/src/SendEmail.cs

@@ -54,16 +54,6 @@ protected override async Task Handle(SendEmail request, CancellationToken cancel
                 Subject = subject
             };
 
-            var headers = request.Headers ?? emailOptions.DefaultHeaders;
-
-            if (headers != null)
-            {
-                foreach (var (field, value) in headers)
-                {
-                    message.Headers.Add(field, value);
-                }
-            }
-
             if (!string.IsNullOrWhiteSpace(request.BccRecipient))
             {
                 message.Bcc.Add(new MailboxAddress(request.BccRecipient, request.BccRecipient));

src/Email/test/SendEmailWithMockedClientTests.cs

@@ -0,0 +1,49 @@
+// Copyright (c) Fusonic GmbH. All rights reserved.
+// Licensed under the MIT License. See LICENSE file in the project root for license information.
+
+using System.Globalization;
+using FluentAssertions;
+using Fusonic.Extensions.Email.Tests.Models;
+using MimeKit;
+using NSubstitute;
+using NSubstitute.ClearExtensions;
+using SimpleInjector;
+using Xunit;
+
+namespace Fusonic.Extensions.Email.Tests;
+
+public class SendEmailWithMockedClientTests : TestBase<SendEmailWithMockedClientTests.SendEmailFixture>
+{
+    private readonly ISmtpClient smtpClient;
+
+    public SendEmailWithMockedClientTests(SendEmailFixture fixture) : base(fixture)
+    {
+        smtpClient = GetInstance<ISmtpClient>();
+        smtpClient.ClearSubstitute();
+    }
+
+    [Fact]
+    public async Task SendEmail_StandardHeadersOverwritten()
+    {
+        await smtpClient.SendMailAsync(Arg.Do<MimeMessage>(ValidateEmail));
+
+        var model = new SendEmailTestEmailViewModel { SomeField = "Some field." };
+        await SendAsync(new SendEmail("recipient@fusonic.net", "The Recipient", new CultureInfo("de-AT"), model, Headers: new Dictionary<string, string> { ["Message-Id"] = "value" }));
+
+        await smtpClient.Received(1).SendMailAsync(Arg.Any<MimeMessage>());
+
+        static void ValidateEmail(MimeMessage email)
+        {
+            email.Headers.Should().ContainSingle(s => s.Field.Equals("Message-Id", StringComparison.OrdinalIgnoreCase));
+            email.Headers["Message-Id"].Should().Be("value");
+        }
+    }
+
+    public class SendEmailFixture : TestFixture
+    {
+        protected override void RegisterDependencies(Container container)
+        {
+            container.RegisterSingleton(() => Substitute.For<ISmtpClient>());
+        }
+    }
+}