Randy Bush via Postfix-users:
> On Wed, 21 Jan 2026 03:17:25 -0800, Matus UHLAR - fantomas via Postfix-users
> wrote:
>
> > If you forward recipients of bogus.com to well-known smtp server, and
> > that server is able to reject non-existing users, you can use
> > reject_unverified_recipient
> > as described in
> > http://www.postfix.org/ADDRESS_VERIFICATION_README.html
>
> which is really helpful and works quite well, but i could use a bit more
> guidance
>
> 2026-01-24T23:05:06.468429+00:00 m0 postfix/smtp[198459]: 2224EFF995:
> to=<[email protected]>, relay=my-relay.com[2001:418:19::63]:25, delay=1.3,
> delays=0.51/0.02/0.74/0.07, dsn=5.0.0, status=bounced (host
> my-relay.com[2001:418:19::63] said: 550 unknown user (in reply to RCPT TO
> command))
>
> `status=bounced` means that the spam caused the system to try to send a
> bounce back to the sender^Hspammer.
>
> i realize that tradidionally one wants a human sender to know that
> claire emimigrated to santiago in 2014.
>
> on the other hand, spam predominates and the sender is often spoofed or
> just a commercial machine gun. so the bounce is just adding to global
> pollution.
>
> what is the wise path? is there one, or is this rock and hard place?
You can use reject_unlisted_sender selectively in smtpd_xxx_restrictions
(and smtpd_reject_unlisted_sender=yes globally) to reject mail from
an address that does not exist. It allows recipients that match
local_recipient_maps, virtual_alias_maps, relay_recipient_maps, and
virtual_mailbox_maps and rejects other senders.
It works like reject_unlisted_recipient in smtpd_xxx_restrictions
(and smtpd_reject_unlisted_recipient=yes globally).
sender address valiation is not enabled by default.
Wietse
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