On Thu, Apr 07, 2022 at 04:55:26PM +0000, Pedro David Marco wrote:
> I have destinations not accepting email with a 451 return code. Some
> of them are being sent by postfix to the smtp_fallback_relay and some
> of them are just sent to the deferred queue... Probably i am
> misunderstanding Postfix documentation but... What is exactly the
> Postfix criteria about using smtp_fallback_relay ????
When at least one envelope recipient soft fails for all attempted
connections and/or SMTP sessions, then connections are attempted to any
configured fallback relays (for such remaining envelope recipients).
No detailed analysis is possible without logs. If you post all the
relevant log entries (including relevant messages from the "smtp"
processes with same "pid" as the final defer log entry) then it'll be
possible to disect the sequence of events for a particular delivery
attempt.
You may find the "collate" script useful:
https://github.com/vdukhovni/postfix/tree/master/postfix/auxiliary/collate
--
Viktor.
