The problem appears to be that MailMate does not find any recipient headers in the message. In other words, it's unrelated to the servers/accounts in play. Maybe the redirect address is somehow invalid and therefore stripped by MailMate when generating the message. What is the value used in the redirect rule? You can obfuscate it to not share the address on this open forum. Alternatively, send it via “Help ▸ Send Feedback” in MailMate.

Yo Benny,

I do not expect immediate responses at all for tickets. I appreciate that you even bother to offer support for issues unrelated to the product. I am very thankful.

I think I may have tracked down the problem. Re-direct fails when the "Resent-From" header contains UT8 characters. For example, this works -

Resent-From: "abc" abc@def.com

This does not work -

Resent-From: "abc =?utf-8?b?YWJj?=" abc@def.com

Are you able to reproduce?

KQ

That didn't help me reproduce the issue. I've got an æ in my name and therefore all address headers contain UTF8 and I'm not seeing this issue.

Could you send me this file: ~/Library/Application Support/MailMate/Mailboxes.plist

Thanks in advance!