As mentioned earlier, recipient address verification may be
useful to block mail for undeliverable recipients on a mail relay
host that does not have a list of all valid recipient addresses.
This can help to prevent the mail queue from filling up with
MAILER-DAEMON messages.
Recipient address verification is relatively straightforward
and there are no surprises. If a recipient probe fails, then Postfix
rejects mail for the recipient address. If a recipient probe
succeeds, then Postfix accepts mail for the recipient address.
By default, address verification results are not saved. To avoid
probing the same address repeatedly, you can store the result in a
persistent database as described later.
/etc/postfix/
main.cf:
smtpd_recipient_restrictions =
permit_mynetworks
reject_unauth_destination
...
reject_unknown_recipient_domain
reject_unverified_recipient
...
The "
reject_unknown_recipient_domain" restriction blocks mail
for non-existent domains. Putting this before "
reject_unverified_recipient"
avoids the overhead of generating unnecessary probe messages.
The
unverified_recipient_reject_code parameter (default 450)
specifies how Postfix replies when a recipient address is known to
bounce. Change this setting into 550 when you trust Postfix's
judgments.
