Hi there,

On Mon, 3 Jul 2017, Antony Stone wrote:
On Monday 03 July 2017 at 22:27:44, Gregory Nowak wrote:
> > On Mon, Jul 03, 2017 at 07:09:29PM +0200, Joachim Fahrner wrote:
> >
> > > I get lots of those errors in my postfix log:
> > >
> > > Jul 3 18:09:16 server postfix/smtpd[2840]: NOQUEUE: reject: RCPT
> > > from tupac2.dyne.org[178.62.188.7]: 450 4.7.1 <tupac2.dyne.org>:
> > > Helo command rejected: Host not found;
> > > from=<dng-bounces@???> to=<jf@???> proto=ESMTP
> > > helo=<tupac2.dyne.org>
> > >
> > > Is there some configuration problem with the list mail server?
> >
> > I'm not seeing this here, and the A record for tupac2.dyne.org
> > resolves correctly. Could there be a DNS issue on your end perhaps?
>
> tupac2.dyne.org resolves here perfectly well too, however surely the problem
> being reported by that error message is that the machine tupac2.dyne.org
> cannot resolve fahrner.name (which also resolves here perfectly okay)?

No, the issue does seem to at or before the 'helo' command stage, but
the error message isn't terribly clear to me because I'm a Sendmail
user. :/ Whatever isn't found (presumably not found by the DNS server
which Postfix is using) it isn't the envelope recipient, which has not
been established at the 'helo' stage.

The nameservers for dyne.org look fine, and I see no problems (in the
UK, with Sendmail & BIND).

In a case like this I'd look at my nameserver logs. If you don't use
a local nameserver you could set up a caching-only server just so it
can log things. That might even fix the probelm. :) Alternatively you
could run a tool like tcpdump to record the traffic and then display
it e.g. with Ethereal.

--

73,
Ged.