[155110] in North American Network Operators' Group
Re: Is Hotmail in the habit of ignoring MX records?
daemon@ATHENA.MIT.EDU (Jimmy Hess)
Thu Jul 26 03:39:15 2012
In-Reply-To: <20120726071441.GA11199@metron.com>
Date: Thu, 26 Jul 2012 02:38:31 -0500
From: Jimmy Hess <mysidia@gmail.com>
To: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On 7/26/12, Lou Katz <lou@metron.com> wrote:
> One of my users has reported incoming mail failures, which I finally
> tracked down. It turned out that Hotmail has seen fit to send the mail
> to his domain's A record machine, despite the fact that he has valid MX
> records.
You looked in the mail headers and saw hotmail's mail server do that,
or the From address/return path just happens to be hotmail?
I would ask for a specific example of a domain name in which that
seems to happen, and exact DNS zone contents.
I am sure that Hotmail does not ignore MX in general, unless they
just broke something; many domains require MX processing and A record
to properly be ignored for mail to be accepted. But there may be
something else going on with a specific domain or DNS
queries/responses from its nameservers, that results in MX being
ignored or unavailable, resulting in a fallback to 'lookup A'.
An example could be some dns issue such as slow response to MX query,
'MX to a CNAME', 'MX to an invalid label that looks like an IP', MX
DNS response packet too large,
....
--
-JH
