Re: MX question - ReadList.com

5 msg	client.c Assertion Failure
17 msg	TXT record problem (Timed out)
2 msg	Problem with cname target pointing to wildcard ...
4 msg	multiple domains on same ip adresses
3 msg	Use of 'notify' and 'also-notify'

MX question
\ Jim (22 Aug 2006)
. \ base60 (22 Aug 2006)
. \ Jim (22 Aug 2006)
. \ Dawn Connelly (22 Aug 2006)
. \ Barry Margolin (22 Aug 2006)
. . \ Chris Thompson (23 Aug 2006)
. \ base60 (22 Aug 2006)

9 msg	Chaining CNAMEs?
2 msg	enforced delegation only
3 msg	slow IXFR updates
1 msg	SV: rndc connection problems
7 msg	Hosting own domain - newb questions.
2 msg	rndc connection problems
8 msg	SDB Backend for Bind
1 msg	Lookup slowness after ~5 minutes
3 msg	Question about a dot in hostname
3 msg	Dynamic updates stopped working
3 msg	named will not start
2 msg	Dual stack to IPv4 conversion
3 msg	Bind 9 allow-recursion limited to localhost
3 msg	2 A records, 2 PTR records, just 1 IP - is this...

Subject:	Re: MX question
Group:	Bind-users
From:	Chris Thompson
Date:	23 Aug 2006

On Aug 22 2006, Barry Margolin wrote:

>In article <ecf9l4$cjq$1>, "Jim" <jim> wrote:
>
>> hi folks,
>>
>> I have a customer's dns server (bind - not sure of version) not able to
>> resolve my mx records to one of my zones. Here are my current records:
>>
>> 100 mydomain.com.s5a1.psmtp.com.
>> 200 mydomain.com.s5a2.psmtp.com.
>>
>> I'm being told from the customer that my mx records are formatted
>> improperly. His argument is that his version of bind is unable resolve the
>> mx record when the domain name _does not_ appear at the end of the record
>> (ie s5a1.psmtp.com.mydomain.com would work fine for him).
>>
>> Is this is a known problem with some versions of bind?
>> Can someone point me to documentation that tells me proper/illegal syntax
>> for my mx records.
>
>MX records are allowed to point to any name that has an A record. Is he
>claiming that the MX record has to point to a name in the same domain?
>There has never been such a requirement, and there are many domains that
>do not fit that criterion.

On the assumption that the OP is not obfuscating his example too much ...

mydomain.com.s5a1.psmtp.com and mydomain.com.s5a2.psmtp.com do resolve
to A records for 64.18.4.10 and 64.18.4.11 respectively. But they do so
by virtue of wildcard A records, and reverse lookup of the IP addresses
yields PTR records containing "*.s5a1.psmtp.com" and "*.s5a2.psmtp.com".

There's nothing technically invalid about that[*], but it could well
upset an MTA using a sufficiently paranoid resolver.

[*] ... or is there? The target of an MX is meant to be a canonical name.
not (e.g.) a CNAME. Does using a wildcard address record mean that it
isn't <<really>> a canonical name?

In any case, I don't see the point. Using different aliases of an address
in MX records for different mail domains isn't going to get you anything
useful at the SMTP level, AFAICS.

--
Chris Thompson
Email: cet1