I ran into a mail problem that I didn't notice after my recent upgrade to #buster. When I would compose a new mail and send it via opensmtpd over the smarthosts I use, everything was fine. But when I replied to a mail in Emacs with a 'From:' that differs from user-mail-address, Emacs happily just used the latter when handing over the mail to "sendmail" and I think that was not the case before.

I think that's a change in Emacs 27 to the default value of message-sendmail-envelope-from. I can't prove that's the culprit, but the same Emacs/message config was used before the upgrade. Or maybe the newer opensmtpd version is doing some things differently, I don't know. Anyway, setting the variable to 'header fixes things. #emacs #emacs27 #opensmtpd