Hello again,
doobry wrote:
It's only an option when possible to be configured server-wide (by default) as users will not add it to their sieve redirect rules for sure. [...]
So I searched for a way to detect that the bounce message is a reply to a sieve redirect.
I think I found a superior solution: setting sieve_redirect_envelope_from = "<noreply-sieve@domain.org>", which is either a mailbox managed by the admins or an alias to /dev/null. This eliminates the problem with mail loops that orig_recipient invented while it still doesn't break DMARC.
It means that the bounce replies don't reach the original sender, but that's out of scope anyway with anything but sieve_redirect_envelope_from = sender.
I don't see any major problems with setting the envelope sender for sieve redirects to a fixed admin-controlled address apart from the mentioned side-effect that bounce replies to sieve redirects getting lost. Do I oversee something?
Kind regards, doobry