From: mouss (mlist.onlyfree.fr)
Date: Wed Jul 04 2007 - 16:17:48 CDT

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Rick Zeman wrote:
> On 7/3/07, mouss <mlist.onlyfree.fr> wrote:
>> Joey wrote:
>> > Is there an RFC requiring mail servers to have forward & reverse DNS ?
>> >
>>
>> yes. 1912, 1033, ... etc.
>
> Where in either of them does it say a mail server HAS to have a
> reverse DNS vs how to do it if you want to? If there's a hard and
> fast requirement (vs best practices), that's new news to me...
>
>

The first paragraph of section 2.1 in RFC 1912 is crystal clear (every
Internet-reachable host ...., make sure your PTR and A records..., For
every IP address... ).

RFC 1033 has an "instructions" section. see "Adding a host".

The "correct" setting is:
- the client IP resolves to a hostname
- the first returned hostname should resolve to n IPs (n>=1)
- one of these n IPs is the client IP

whether this be a mail client or not. my registrar doesn't allow whois
queries from "bad" clients and I find this good. If it was not for the
performance overhead, every network service should/may reject
misconfigured clients...

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