Alex:
> Hi,
>
> >> ? ? Received: from zaphod.chipchaps.com (unknown [65.182.186.13])
> >>
> >> It says 'unknown', but 65.182.186.13 does resolve, to chipchaps.com (a
> >> spam site), which resolves back to 65.182.186.12. Is this where the
> >> problem is?
> >
> > The definition of an "unknown" client hostname is given in
> > http://www.postfix.org/postconf.5.html#reject_unknown_client_hostname
> > which, as the name suggests, rejects mail from a client with a hostname
> > that Postfix considers "unknown".
>
> Is it common practice to have that restriction in a production environment?
Yes, if the tolerance for spam is worse than the tolerance for
mail not received.
[speculation deleted]
> Is there a way to log these specific failures so I can get a better
> idea of under what circumstances they occur in my environment?
Postfix logs a warning when the reverse name does not resolve, or
when the reverse name resolves to the wrong address:
warning: 1.2.3.4: hostname example.com verification failed:
Host not found, try again
warning: 1.2.3.4: address not listed for hostname example.com
When you report a problem, it is a good idea to look at the
warning messages in the Postfix logfile.
Wietse
