RRs for mail server

[Barry Margolin]

In article <bj36gq$205t$1 at sf1.isc.org>,
Jukka Salmi  <jukka-usenet at 2003.salmi.ch> wrote:
>I'm setting up resource records for a mail server. So far I have:
>
>[...]
>example.       IN  MX  mail.example.

You need a preference number after "MX".

>foo.example.   IN  A   1.2.3.4
>mail.example.  IN  A   1.2.3.4
>[...]
>4.3.2.1.in-addr.arpa  IN  PTR  foo.example.

There should be a "." after "arpa".

>[...]
>
>The mail server uses mail.example as HELO hostname when sending mail.
>
>I'm not sure if this is a valid setup, because if the remote mail server
>does a reverse lookup for mail.example and then looks up the A record
>for the address it got, he will get foo.example (and not mail.example
>as used in HELO). If this is a problem I should probably change the MX

There's no requirement that the name in the HELO command match the name in
the PTR record.  They often don't match when the mail server is multi-homed
and therefore has multiple addresses, or as in cases like yours where the
server simply has multiple names.

However, there are some sites that do this type of check anyway, as a form
of spam blocking.  So if you can make them consistent, it's not a bad idea.

>record to
>
>example.       IN  MX  foo.example.

That's a good idea.

-- 
Barry Margolin, barry.margolin at level3.com
Level(3), Woburn, MA
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