David Mehler:
> Mar 20 18:19:12 mail postfix/smtpd[53636]: NOQUEUE: reject: RCPT from
> xxx.xxx.xxx.xxx[xxx.xxx.xxx.xxx]: 550 5.7.1 <mail.xx.xxx.xxx>: Helo
> command rejected: Host not found; from=<x...@xxx.xxx> to=<x...@xxx.xxx>
> proto=ESMTP helo=<mail.xx.xxx.xxx>
As documented ("man 5 postconf", or www.postfix.org/postconf.5.html):
reject_unknown_helo_hostname
Reject the request when the HELO or EHLO hostname has no DNS A
or MX record.
> Googling brought me to an issue where this was discussed pointing to
> reject_unknown_helo_hostname as the likely culprit since the mail
> server a and ptr records are working fine, but the helo it's sending
> doesn't reverse ptr.
Nope, this has nothing to do with PTR records. It's A and MX (and
AAAA in the case that IPv6 is turned on).
> The fix was a suggestion of commenting out
> reject_unknown_helo_hostname checking:
>
> https://serverfault.com/questions/922935/why-does-postfix-say-helo-command-rejected-host-not-found-when-dig-finds-the
> http://www.postfix.org/postconf.5.html#reject_invalid_helo_hostname
>
> I don't want to blanket disable reject_unknown_helo_hostname is there
> a way I can set a helo exception for this one host/sender?
Yes you can.
smtpd_recipient_restrictions =
...
reject_unauth_destination
check_client_access inline:{example.com=permit}
reject_unknown_helo_hostname
But it is better to stop using reject_unknown_helo_hostname because
the are many misconfigured servers that send legitimat mail.
Wietse
