Problem with "temporary failure at return MX check"


I recently installed a new mail server with postfix 2.8.2.
This machine replaced an older one, with nearly the same features and

Since that, however, I'm experimenting problems to send
emails to only one destination. Logs show:

Sep 28 18:51:27 mailserver
postfix/smtp[21279]: 3418C61EE1: enabling PIX workarounds: disable_esmtp
delay_dotcrlf for[]:25

Sep 28 18:51:47 mailserver
postfix/smtp[21279]: 3418C61EE1: to=,[]:25,
delay=3207, delays=3167/0/20/20, dsn=4.0.0, status=deferred (host[] said: 421 DNS temporary failure at return MX check,
try again later (#4.3.0) (in reply to MAIL FROM command))

I started
checking for DNS problems. Everything seems to be correct, both A and MX
records, as well as reverse resolution.

I already tried to disable pix
workarounds, as older version didn't have this feature and worked well, but
there were no changes in results. Can somebody please help me on this

Thank you!



Re: Problem with "temporary failure at return MX check"

By Noel Jones at 09/30/2011 - 12:15

On 9/30/2011 10:49 AM, ajm wrote:
The server at is refusing your mail; only they can
give you an authoritative answer why.

From the message returned, I assume they are doing an MX lookup on
the MAIL FROM domain, and that lookup fails. This doesn't have
anything to do with the pix workarounds.

-- Noel Jones

Re: Problem with "temporary failure at return MX check"

By ajm at 09/30/2011 - 12:23

If pix workarounds are out of question, I think just DNS remains.

On DNS I have currently:

nslookup -query=MX domain - returns only an MX_server - the correct one
nslookup MX_server - returns the correct ip address
nslookup ip_address - returns the name of a machine from the same
domain, but not the MX_server.

Even if the reverse resolution does not point to exactly the same name
(there are CNAMEs), it resolves to the same domain.
I thought it would be enough, as I did never need more than this before,
but then this is probably the problem.

Thank you for your help!

On Fri, 30 Sep 2011 11:15:07 -0500, Noel Jones < ... at megan dot>

Re: Problem with "temporary failure at return MX check"

By Noel Jones at 09/30/2011 - 13:19

[please don't top post]

On 9/30/2011 11:23 AM, ajm wrote:
The error indicated a temporary lookup failure. Just because
lookups work for you doesn't mean they work for everyone.

You'll need to check with the destination about their idea of close

-- Noel Jones

Re: Problem with "temporary failure at return MX check"

By Robert Schetterer at 09/30/2011 - 12:41

Am 30.09.2011 18:23, schrieb ajm:
dont top post
use dig for lookups
better with real world examples
mx entries in dns are no secrets

after all i think your question was allready answered by Noel