I observed a strange (to me) behavior and id like a better understanding
of what is happening.
I have smtpd_reject_unlisted_recipient = no
I do not have reject_unlisted_recipient in any of the
smtpd_*_restrictions
I have a milter that checks the rcpt address against SQL and returns a
custom reject message if user doesn't exist
Pretend my server is example.com and spammer.com is someone fictitious.
If i get an email From: u...@spammer.com, To: u...@example.com then the
milter gives the custom reject message.
However if they send an email with both addresses from my domain like
From: u...@example.com, To: u...@example.com then postfix issues the
default reject:
NOQUEUE: reject: RCPT from unknown[196.188.245.169]: 550 5.1.0
<u...@example.com>: Sender address rejected: User unknown in virtual
mailbox table; from=<u...@example.com> to=<u...@example.com> proto=ESMTP
helo=<[196.188.245.169]>
In that case is postfix rejecting based on the From: or the To: not
being a valid user?
Why is postfix checking either when smtpd_reject_unlisted_recipient =
no?
Is there a built in check on the From: address that does something if
the From: domain matches one of virtual_mailbox_domains? If so what is
actually happening behind the scenes?
