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Some MX or DNS issue - we cannot send or receive mail to/from schools.nyc.gov

We have a major client schools.nyc.gov and all of the sudden we cannot send or receive email with them.  It started this weekend and I received reports from my users on my domain saying that email TO schools.nyc.gov were bouncing.  (I am new here and still figuring out the systems)

I thought that this problem was our FirstClass email server so I called tech support and he told me that the log below shows that it's on the schools.nyc.gov side.

Anyway please read the rest but I need some clue as to where to look and what to do.   I have called the schools.nyc.gov helpdesk and they brushed me off.  They finally put in a ticket but I feel like they aren't taking it seriously and they think it's on my side.  I'm not even sure at this point.

I investigated this and got this log out of our POS mail server FirstClass:

[2008/10/21 08:07:18] SMTPMsg-34: Processing message 10/475
[2008/10/21 08:07:19] SMTPMsg-34: Relay smtp1.nycenet.edu (0xa59b6865) serves domain schools.nyc.gov
[2008/10/21 08:07:19] SMTPMsg-34: Delivering message to schools.nyc.gov (0xa59b6865)
[2008/10/21 08:07:35] SMTPMsg-34: Rcv: 220 op0iron01.schools.nyc.gov ESMTP
[2008/10/21 08:07:35] SMTPMsg-34: Snd: EHLO mbeabbs.mathsolutions.com
[2008/10/21 08:07:35] SMTPMsg-34: Rcv: 250-op0iron01.schools.nyc.gov
[2008/10/21 08:07:35] SMTPMsg-34: Rcv: 250-8BITMIME
[2008/10/21 08:07:35] SMTPMsg-34: Rcv: 250 SIZE 10485760
[2008/10/21 08:07:35] SMTPMsg-34: Snd: MAIL FROM:<[ mailto:cchambers@mathsolutions.com ]cchambers@mathsolutions.com> SIZE=3070
[2008/10/21 08:07:50] SMTPMsg-34: Rcv: 451 #4.1.8 Domain of sender address <[ mailto:cchambers@mathsolutions.com ]cchambers@mathsolutions.com> does not resolve
[2008/10/21 08:07:50] SMTPMsg-34: Snd: QUIT
[2008/10/21 08:07:50] SMTPMsg-34: Looking for additional mail exchangers
[2008/10/21 08:07:50] SMTPMsg-34: Found relay smtpout.nycenet.edu (0xa59b69fe) for domain schools.nyc.gov
[2008/10/21 08:07:50] SMTPMsg-34: Delivering message to schools.nyc.gov (0xa59b69fe)
[2008/10/21 08:08:06] SMTPMsg-34: Rcv: 220 op0iron02.schools.nyc.gov ESMTP
[2008/10/21 08:08:06] SMTPMsg-34: Snd: EHLO mbeabbs.mathsolutions.com
[2008/10/21 08:08:06] SMTPMsg-34: Rcv: 250-op0iron02.schools.nyc.gov
[2008/10/21 08:08:06] SMTPMsg-34: Rcv: 250-8BITMIME
[2008/10/21 08:08:06] SMTPMsg-34: Rcv: 250 SIZE 10485760
[2008/10/21 08:08:06] SMTPMsg-34: Snd: MAIL FROM:<[ mailto:cchambers@mathsolutions.com ]cchambers@mathsolutions.com> SIZE=3070
[2008/10/21 08:08:21] SMTPMsg-34: Rcv: 451 #4.1.8 Domain of sender address <[ mailto:cchambers@mathsolutions.com ]cchambers@mathsolutions.com> does not resolve
[2008/10/21 08:08:21] SMTPMsg-34: Snd: QUIT
[2008/10/21 08:08:21] SMTPMsg-34: Looking for additional mail exchangers
[2008/10/21 08:08:21] SMTPMsg-34: No additional mail exchangers found, delaying recipients
[2008/10/21 08:08:21] SMTPMsg-34: Delaying recipient "JHugule@schools.nyc.gov"
[2008/10/21 08:08:21] SMTPMsg-34: Updating message history Who="JHugule@schools.nyc.gov" When=-987545995 What=22
[2008/10/21 08:08:21] SMTPMsg-34: Done processing message

So it looks like to me that they are looking up our domain and saying it's not resolving correctly.

I then looked up our MX records and they are correct :

0      mbeabbs.mathsolutions.com            
15      groups.mathsolutions.com                  
20      caseyjones.dundee.net                  
30      caseyjones.dundee.net            
40      mail.mathsolutions.com      

Our mail comes into Spamassassin then Postfix and then into FirstClass.  

Then the plot thickens because I get a call from a user on the schools.nyc.gov network and they are trying to send us email and it's bouncing as well.  I asked her to forward me the bounce messages and this is what she is getting:

From:   System Administrator
Sent:   Tuesday, October 21, 2008 8:37 PM
To:     nrizzo@mathsolutions.com
Subject:        Undeliverable: Summer Geometry course

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

      Subject:  Summer Geometry course
      Sent:     10/19/2008 8:07 PM

The following recipient(s) could not be reached:

      nrizzo@mathsolutions.com on 10/21/2008 8:37 PM
            The e-mail system was unable to deliver the message, but did not report a specific reason.  Check the address and try again.  If it still fails, contact your system administrator.

            < schools.nyc.gov #5.0.0 smtp; 5.4.7 - Delivery expired (message too old) 'DNS Soft Error looking up mathsolutions.com (MX) while asking recursive_nameserver0.parent. Error was: unable to reach nameserver on any valid IP' (delivery attempts: 0)>
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1 Solution
MX records may be OK, but does rDNS work for "mathsolutions.com "?

The second part of your post seems to indicate a general DNS problem with mathsolutions.com; does mail from other parties go OK in both directions?
norcaltyAuthor Commented:
I can send and receive email from my gmail account to mathsolutions.com so it seems like it works.
OK, so schools.nyc.gov fails in doing rDNS lookups for incoming and in resolving mathsolutions.com for outgoing messages. How is DNS handled for schools.nyc.gov?
norcaltyAuthor Commented:
It ended up being that for some reason the nyc.gov system is blocking a huge portion of the internet on the West Coast.

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