[Gllug] E-Mail screening and reverse DNS

[Nix]

On Sun, 11 Jun 2006, Paul Cupis spake:
> Nix wrote:
>> Why should it need to do that? Sites rejecting SMTP connections
>> where forward != reverse DNS (as opposed to those where forward and
>> reverse do not resolve to the same IP) will reject a very large
>> proportion of legitimate mail, including mail from many *major*
>> mailing lists.
> 
> "Reverse doesn't resolve to the same IP" ?

Badly phrased on my part, perhaps, but:

nix at hades 951 /home/nix% host -t mx esperi.org.uk
esperi.org.uk mail is handled by 5 mail.esperi.org.uk.
[...]

nix at hades 953 /home/nix% host mail.esperi.org.uk
mail.esperi.org.uk has address 194.247.41.52       <----

nix at hades 955 /home/nix% host 194.247.41.52
52.41.247.194.in-addr.arpa domain name pointer 41-052.adsl.zetnet.co.uk.

nix at hades 956 /home/nix% host 41-052.adsl.zetnet.co.uk.
41-052.adsl.zetnet.co.uk has address 194.247.41.52 <----


The fact that the reverse resolution of my MX record yields a name
different from that on the MX record is irrelevant (it had better be:
that machine has half a dozen names in addition to the nasty automatic
reverse-resolution-only one Zetnet assigned).

What matters is those two arrowed lines: the name acquired from
reverse-resolution of my IP address forward-resolves to the same
address in its turn

-- 
`Voting for any American political party is fundamentally
 incomprehensible.' --- Vadik
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