On Thu, 1 Dec 2022 at 15:49, Matus UHLAR - fantomas <uh...@fantomas.sk> wrote:
> On 01.12.22 15:23, David Dolan wrote: > >We have two customers who we're unable to receive email from. > >It's failing the helo lookup as it can't resolve the hostname in the helo > >message. > >Helo command rejected: Host not found; > > The issued hostname is logged just prior to this text. > You skipped the most impotant info here. > > This is the full line NOQUEUE: reject: RCPT from unknown[103.246.251.109]: 450 4.7.1 < wx-use2.prod.hydra.sophos.com>: Helo command rejected: Host not found; from=<#############> to=<#############> proto=ESMTP helo=< wx-use2.prod.hydra.sophos.com> > >The postfix configuration for helo checks is as follows. It's failing on > >reject_unknown_helo_hostname > > > >smtpd_helo_required = yes > >smtpd_helo_restrictions = > >reject_non_fqdn_helo_hostname > >reject_invalid_helo_hostname > >reject_unknown_helo_hostname > > you should be able to explicitly allow IP addresses of your customers. > On ports 465/587, these checks even should not be applied as they (should) > explicitly require authentication > > >The hostnames in the helo messages are resolvable with the PTR and A > record. > >However there are 32 A records. I don't know if that's an issue which > >causes a problem with the verification. > > there is no "A" record as "Host not found" means that the hostname > provided > does not exist. > > reject_invalid_helo_hostname and reject_unknown_helo_hostname try to > resolve > the helo string and report it in the error message and in the logs: > > ehlo trest.fantomas.sk > > Dec 1 16:44:31 fantomas postfix/smtpd[30059]: NOQUEUE: reject: RCPT from > example.com[192.0.2.1]: 450 4.7.1 <trest.fantomas.sk>: Helo command > rejected: Host not found; > from=<uh...@example.com> to=<uh...@fantomas.sk> proto=ESMTP helo=< > trest.fantomas.sk> > > >Maybe it can't match the IP address with the hostname as it does a round > >robin dns lookup and doesn't find the IP which the message arrived from? > > no. > > -- > Matus UHLAR - fantomas, uh...@fantomas.sk ; http://www.fantomas.sk/ > Warning: I wish NOT to receive e-mail advertising to this address. > Varovanie: na tuto adresu chcem NEDOSTAVAT akukolvek reklamnu postu. > The early bird may get the worm, but the second mouse gets the cheese. >
