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? It appears to be the third case here, that the name->address mapping does not match the client IP address. Could this be from a legitimate cause, or typically intentionally to be evasive? Could it be found in a legitimate dynamic environment, such as at an ISP? 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? I'm currently rejecting the following, in this order: reject_non_fqdn_sender, reject_non_fqdn_recipient, reject_unknown_sender_domain, reject_unknown_recipient_domain, reject_unauth_pipelining, reject_invalid_hostname, reject_non_fqdn_hostname, reject_unauth_destination, reject_maps_rbl, Thanks, Alex