Re: [exim] [OT] Why att.net has DNS failure?

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Autor: W B Hacker
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A: exim users
Assumpte: Re: [exim] [OT] Why att.net has DNS failure?
Bill Moseley wrote:
> On Fri, Jan 26, 2007 at 06:13:11AM +0800, W B Hacker wrote:
>> Digging @ns1.hank.org and @ns2.hank.org finds that the record type is odd.
>> i.e. there is an 'A' record as well as an 'MX' record for the mailserver, but no
>> 'A' record for the bare domain.tld.
>>
>> If it were my domain, I would:
>>
>> - add an 'A' record for whmoseley.com
>
> That's what I was wondering. But, is that required?
> I mean, isn't this everything that should be needed to find the
> machine?


That depends to some extent on the software ATT is using.

Understanding that all you want to publish is the mailserver, it is still, just
IMNSHO, not necessarily a 'good thing' to have no 'A' record for the bare
<domain>.<tld>. i haven't researched whether it is is / is not a standards
violation, but lots of things rely on the'A' recpord for the 'raw'
<domain>.<tld> and some of these MAY be used by SOME mailservers - ident
callouts, to name one.

I am also of the opinion that having BOTH an 'A' AND an 'MX' entry, plus, ISTR,
the (only?) SOA attached exclusively to the mailserver only is not what folks
expect either.

>
>     $ dig mx whmoseley.com.
>     ;; ANSWER SECTION:
>     whmoseley.com.          86400   IN      MX      5 mail.whmoseley.com.

>
>     $ dig A mail.whmoseley.com.
>     ;; ANSWER SECTION:
>     mail.whmoseley.com.     86400   IN      A       63.205.225.170

>
> Clearly it's worked for all other senders for a few years. Maybe
> att.net has one picky MTA that doing extra tests on the DNS.
>
>
>> - pull the 'A' record for mail.whmoseley.com
>>
>> - optionally add an 'MX' record for mx.whmoseley.com
>>      (some folks do seek that....)

>
> Do you mean literally "mx." ?
>


Actually yes. One can easily have both 'mail.<domain>.<tld>' and
'mx.<domain>.<tld>' in the record - both as 'MX' entries, and with the same IP
and priority.

Last year on one of our servers we did have a problem with a correspondent that
was looking for the unexpected one. Providing both solved that issue for us.

No idea how common that might be - it was only the one sender, but one we needed
to correspond with on a regular basis.

But AFAIK, mx.<whatever> and mail.<whatever> MX records are harmless, your
entries less so.

QED.


Bill