Wietse Venema via Postfix-users:
> Rob Foehl via Postfix-users:
> > There's a particularly obnoxious ESP that won't take no for an answer,
> > repeatedly retrying delivery attempts despite 5xx responses -- unless
> > "no" is spelled exactly "550 5.1.1 ...", apparently.
>
> That's what Postfix says for an unknon unknown recipient:
>
> rcpt to:<xx...@porcupine.org>
> 550 5.1.1 <xx...@porcupine.org>: Recipient address rejected: User unknown
>
> > Cute. I'll just throw that into an access map, and... nope, they get
> > 550 5.0.0, as noted in access(5). Makes sense, but standards compliance
> > isn't a terribly compelling argument when the other side can't be
> > bothered.
> >
> > How can I convince Postfix to stop helping and do what I said?
>
> Are you referring to the second bullet item the section "ENHANCED
> STATUS CODES"?
>
> * When a sender address matches a REJECT action, the Postfix SMTP
> server will transform a recipient DSN status (e.g., 4.1.1-4.1.6)
> into the corresponding sender DSN status, and vice versa.
>
> * When non-address information matches a REJECT action (such as
> the HELO command argument or the client hostname/address), the
> Postfix SMTP server will transform a sender or recipient DSN
> status into a generic non-address DSN status (e.g., 4.0.0).
>
> For good reasons Postfix tries to send replies that are 'RFC correct'.
> That is, it will reply with 5.1.1 only when it detects a 'user
> unknown' condition.
>
> You can fake a 'user unknown' condition with milter-regex (a Milter
> plugin) or with postfwd (a check_policy_service plugin). These can
> reply with "550 5.1.1 user unknown in reply to RCPT TO", when the
> remote SMTP client domain or IP address matches some pattern.
I don't know about milter-regex, but with postfwd you can reply at
RCPT TO time and claim a 'user unknown' status for any reason (in
your case, on who the client is).
smtpd_recipient_instructions =
...
reject_unauth_destiation
check_policy_service inet:127.0.0.1:port
...
With a postfwd "action=550 5.1.1 whatever..." you can then
claim a 'user unknown' condition and Postfix will be bappy
to tell that to the SMTP client.
Wietse
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