Fixing #39

netDumbster/MailMessageExtensions.cs

@@ -17,13 +17,15 @@ public static SmtpMessagePart[] Parts(this MailMessage mailMessage)
 
         foreach (AlternateView alternateView in mailMessage.AlternateViews)
         {
-            var part = new SmtpMessagePart(alternateView.ContentType.ToString(), StreamToString(alternateView.ContentStream));
+            var headers = GetAttachmentHeaders(alternateView);
+            var part = new SmtpMessagePart(headers, StreamToString(alternateView.ContentStream));
             parts.Add(part);
         }
 
         foreach (Attachment attachment in mailMessage.Attachments)
         {
-            var part = new SmtpMessagePart(attachment.ContentType.ToString(), StreamToString(attachment.ContentStream));
+            var headers = GetAttachmentHeaders(attachment);
+            var part = new SmtpMessagePart(headers, StreamToString(attachment.ContentStream));
             parts.Add(part);
         }
 
@@ -35,4 +37,31 @@ private static string StreamToString(Stream stream)
         var reader = new StreamReader(stream);
         return reader.ReadToEnd();
     }
+
+    private static string GetAttachmentHeaders(AttachmentBase attachmentBase)
+    {
+        var headers = new StringBuilder();
+        if (!string.IsNullOrEmpty(attachmentBase.ContentType.ToString()))
+        {
+            headers.AppendLine($"Content-Type: {attachmentBase.ContentType.ToString()}");
+        }
+        if (!string.IsNullOrEmpty(attachmentBase.TransferEncoding.ToString()))
+        {
+            headers.AppendLine($"Content-Transfer-Encoding: {attachmentBase.TransferEncoding.ToString()}");
+        }
+        if (!string.IsNullOrEmpty(attachmentBase.ContentId.ToString()))
+        {
+            headers.AppendLine($"Content-ID: {attachmentBase.ContentId.ToString()}");
+        }
+
+        if (attachmentBase is Attachment attachment)
+        {
+            if (!string.IsNullOrEmpty(attachment.ContentDisposition.ToString()))
+            {
+                headers.AppendLine("Content-Disposition: " + attachment.ContentDisposition.ToString());
+            }
+        }
+
+        return headers.ToString();
+    }
 }

netDumbster/SmtpMessagePart.cs

@@ -9,9 +9,9 @@ namespace netDumbster.smtp;
 /// </summary>
 public class SmtpMessagePart
 {
-    public SmtpMessagePart(string header, string body)
+    public SmtpMessagePart(string headers, string body)
     {
-        HeaderData = header;
+        HeaderData = headers;
         BodyData = body;
     }