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

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