From: Trix on
I was wondering if anyone could come up with an explanation as to why
a reply-to address got mysteriously generated by postfix with the
incorrect details.

A message came in from helen.user(a)example.com. The envelope sender was
identified as helen.lastname(a)example.com in the maillog. The Return-
Path is helen.lastname(a)example.com. The To: address in the message
body is also helen.lastname(a)example.com. However, for some reason, the
Reply-To header has spilt the first element of the envelope sender
address, and then appended our local server address for the domain
part - it looks like "helen(a)smtp1.ourdomain.com,
lastname(a)smtp1.domain.com". The mime type is text/plain, and the
charset is iso-8859-1.

Now, I can understand that a local host part might be appended if the
Reply-To header was empty, although I'm at a loss to think of why it
was empty, why the envelope sender address wasn't used (since I
thought that was the default behaviour if there isn't anything there),
and why on earth the first part was split into two addresses.

Can anyone think of why this happened, other than "one of those
things"? It's only a one-off (that I'm aware of), but I would quite
like to prevent it from happening again.