> > Michael Fox skrev den 2017-09-21 19:52: > > > I have a problem that seems to have started when I upgraded from > Ubuntu > > > 14.04/Postfix 2.11.0 to Ubuntu 16.04/Postfix 3.1.0. It involves the > > > From: > > > and Return Path: addresses seen by recipients of mail sent from a > > > virtual > > > domain on that machine.
This problem turned out to be a DNS issue. The Postfix 3.1.0 machine's virtual domain in the From: address was entered in DNS with a CNAME record pointing to the gateway machine (because they are, indeed, the same address). When it was changed to an A record, the problem went away. Evidently, the user that was certain that the problem only started after the upgrade was, uhm, mistaken. The problem also didn't occur on a separate Postfix 2.11 machine because it's DNS entry was correct. BTW, the mail provider found that the default sendmail config and their own customized config both rewrote the From: header when the From: address was for a domain that had a CNAME record. They said this is a config option in sendmail and they prefer to operate this way. Interesting that my other Postfix machines don't do this, nor do many other large email providers. Michael