On Mon, Nov 22, 2021 at 11:22:33AM -0600, Aaron Poffenberger wrote: > I know this is related to Message-ID because if I go into muttrc(5) > and put `set hostname="example.com"` and send again to > u...@sbcglobal.net, the message goes through without issue.
It's likely not related to the Message-Id. I'd guess that it's related to the envelope from address and / or HELO hostname. maybe this bit: https://gitlab.com/muttmua/mutt/-/blob/master/smtp.c#L435-438 I have never heard of a situation where a host required the hostname portion of the Message-ID header to be resolvable. /w
