Re: DNS and email problem

We've been having similar problems communicating with Comcast and AOL
addresses from our SBS 2003 server and I've followed this thread with
interest. Our problem though seems to be different from what I am
reading here. Basically our situation boils down to Comcast performing
a reverse DNS to the wrong IP address for our mail server but I'm not
sure why they are looking at the wrong IP address in the first place
(I'm a bit of a novice in this area).

MY questions are, what would cause Comcast (and AOL) to bounce back an
error message with an incorrect IP address when a reverse DNS to the
correct IP address would be successful?

For example:

----------
Your message did not reach some or all of the intended recipients.

Subject: Season Pass
Sent: 3/15/2006 8:58 AM

The following recipient(s) could not be reached:

someone@xxxxxxxxxxx on 3/15/2006 8:59 AM
There was a SMTP communication problem with the recipient's
email server. Please contact your system administrator.
<mail.ourserver.com #5.5.0 smtp;521-EHLO/HELO from sender
xx.xxx.xx.30 does not map to mail.ourserver.com in DNS>
----------

The "error" is that our mail server does have a correct PTR and all
appears to be set up correctly but for some reason the error message
shown above lists an incorrect IP address of xx.xxx.xx.30 for our mail
server rather than the correct IP address of xx.xxx.xx.25 (both
addresses ARE static IP's that we have).

Would simply adding a PTR record to my DNS settings pointing
xx.xxx.xx.30 ALSO to mail.ourserver.com correct the problem (even
though my mail server is actually located at the xx.xxx.xx.25 address)?
Would having two PTR's pointing to two different IP addresses on my
server cause any problems elsewhere?

And most importantly, why is the Comcast server performing a reverse
DNS lookup to the wrong IP in the first place? Checking at
www.dnsstuff.com and www.dnsreport.com both show our mail server MX and
PTR records properly with the xx.xxx.xx.25 address.

My apologies if all of this seems confusing or if the answer ends up
being something really simple but I don't have enough experience with
this particular issue to just start changing things in DNS without
asking the questions first. So, any light that anyone can shed on this
for me would be greatly appreciated!

Thank you in advance,

~Shawn


<<snipped>>


"Fred" <apextester@xxxxxxxxxxx> wrote in message
news:1141971004.352681.193310@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Have exactly the same problem with similar environment. Does it with
particular AOL and Comcast E-mail addresses.

Only thing is, I have been unable to recreate the problem using a
Comcast account.

Configured a Comcast account with full spam filtration and no
problem.


Seems there is a wierd spam filter for certain accounts from AOL and
Comcast of which rejects mail sent from an invalid IP address and
domain name association. It may only be doing it with newly created
accounts at Comcast, AOL and others of where a certain query is
executed to filter off illegitmate mail...unfortunately doing it also
to legitimate mail having a bad mail server setting.

Found a link at Comcast of which shed a bit of light having to do
with
reverse DNS, yet am still way in the dark on this:

http://www.comcast.net/help/faq/index.jsp?faq=Email118405

There is manager at the SBS of which allows for configuring the DNS
of
which is yet another gordian knot from Microsoft to deal with.

Will be up late tonight researching this problem.

If you figure it out, please let me know.

Fred

Bryce wrote:
Hello:

I get emails back with this message: (I assume it's coming from our
exchange
server, maybe?)

---------------------------------------------
Your message did not reach some or all of the intended recipients.
Subject: Our company's name
Sent: 3/9/2006 4:24 PM
The following recipient(s) could not be reached:
'macy.fox@xxxxxxxxxxx' on 3/9/2006 4:24 PM
There was a SMTP communication problem with the recipient's email
server.
Please contact your system administrator.
<ourcompany.org #5.5.0 smtp;521-EHLO/HELO from sender 70.xx.xx.xxx
does
not
map to ourcompany.org in DNS>

-------------------------------------


What can I do. It looks like there is a DNS problem on our end?
99% of our email is fine though, but this person can't get anything
to
comcast and sometimes to aol accounts.


Bryce.









.

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