Check the Headers for MessageId before assigning a value in MimeMessa…

…ge .ctor Fixes issue #747
jstedfast · Jan 21, 2022 · 41d643b · 41d643b
1 parent 5e2eb9f
commit 41d643b
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/MimeKit/MimeMessage.cs b/MimeKit/MimeMessage.cs
@@ -226,7 +226,7 @@ public MimeMessage (params object[] args) : this (ParserOptions.Default.Clone ()
 				Date = DateTimeOffset.Now;
 			if (!Headers.Contains (HeaderId.Subject))
 				Subject = string.Empty;
-			if (messageId == null)
+			if (!Headers.Contains (HeaderId.MessageId))
 				MessageId = MimeUtils.GenerateMessageId ();
 		}