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Old 08-07-2008, 08:14 PM
Account for Debian group mail
 
Default Sendmail problem and comcast.net

Hello


We're having a problem sending mail to comcast.net. The message we are
getting is:


Aug 7 12:31:18 smtp sm-mta[22694]: m77JV1iC022684: to=<someuser@comcast.net>, delay=00:00:17, xdelay=00:00:01, mailer=esmtp,
p ri=210588, relay=mx2.comcast.net. [76.96.30.116], dsn=4.0.0, stat=Deferred: 421 IMTA12.emeryville.ca.mail.comcast.net

comcast Reverse DNS failure : Try again later

We are getting this message on different mail servers and comcast.net mail
is stacking up. I have stopped our DNS server and restarted it in case
there is a problem there with no difference.


I do a nslookup on mx2.comcast.net and get:

Non-authoritative answer:
Name: mx2.comcast.net
Address: 76.96.30.116

That checks out... I do a nslookup on
IMTA12.emeryville.ca.mail.comcast.net

and get:

Non-authoritative answer:
Name: IMTA12.emeryville.ca.mail.comcast.net
Address: 76.96.30.30

Which is a different IP address. I'm not sure where it gets the
IMTA12.emeryville.ca.mail.comcast.net address to begin with???


Anyone have any ideas? Does anyone have a phone number to get a hold of
comcast.net administrators?


Thanks,

Ken



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Old 08-07-2008, 08:53 PM
Mike Bird
 
Default Sendmail problem and comcast.net

On Thu August 7 2008 13:14:40 Account for Debian group mail wrote:
> We're having a problem sending mail to comcast.net. The message we are
> getting is:
>
> Aug 7 12:31:18 smtp sm-mta[22694]: m77JV1iC022684:
> to=<someuser@comcast.net>, delay=00:00:17, xdelay=00:00:01, mailer=esmtp, p
> ri=210588, relay=mx2.comcast.net. [76.96.30.116], dsn=4.0.0, stat=Deferred:
> 421 IMTA12.emeryville.ca.mail.comcast.net comcast Reverse DNS failure : Try
> again later

<snip>

> Anyone have any ideas? Does anyone have a phone number to get a hold of
> comcast.net administrators?

The problem is at your end, not Comcast's end. Your 209.102.124.32 server
lacks a reverse DNS entry (PTR record) with value smtp.gssf.org.

Most mail servers block or penalize incoming mail from "servers" with no
reverse DNS or where reverse DNS does not match forward DNS. 99.9% of such
cases are not real servers but rather hacked PCs trying to send spam. The
other 0.1% are real mail servers which by mistake or oversight have DNS
inconsistences - and they should be fixed promptly.

--Mike Bird


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Old 08-07-2008, 11:32 PM
Account for Debian group mail
 
Default Sendmail problem and comcast.net

Mike,

Your right! The reverse DNS file for that IP ranged got toasted by a
FAT finger. Found the error and reload the named server. Thanks for
spotting that!


Thanks again,

Ken


On Thu, 7 Aug 2008, Mike Bird wrote:


On Thu August 7 2008 13:14:40 Account for Debian group mail wrote:

We're having a problem sending mail to comcast.net. The message we are
getting is:

Aug 7 12:31:18 smtp sm-mta[22694]: m77JV1iC022684:
to=<someuser@comcast.net>, delay=00:00:17, xdelay=00:00:01, mailer=esmtp, p
ri=210588, relay=mx2.comcast.net. [76.96.30.116], dsn=4.0.0, stat=Deferred:
421 IMTA12.emeryville.ca.mail.comcast.net comcast Reverse DNS failure : Try
again later


<snip>


Anyone have any ideas? Does anyone have a phone number to get a hold of
comcast.net administrators?


The problem is at your end, not Comcast's end. Your 209.102.124.32 server
lacks a reverse DNS entry (PTR record) with value smtp.gssf.org.

Most mail servers block or penalize incoming mail from "servers" with no
reverse DNS or where reverse DNS does not match forward DNS. 99.9% of such
cases are not real servers but rather hacked PCs trying to send spam. The
other 0.1% are real mail servers which by mistake or oversight have DNS
inconsistences - and they should be fixed promptly.

--Mike Bird


--
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