Emails bouncing back

Over the past few days, I have had users telling me that people whom are trying to email them are getting a bounce message.  When I ask them what it is, they tell me it is this:

The following recipient(s) cannot be reached:
     xxx@888digital.com on 4/6/2009 9:23 AM
            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.
            < jripqe1.jr.local #5.0.0 smtp; 5.1.0 - Unknown address error 554-'5.7.1 This message has been blocked because the return email domain is invalid.(failed to obtain DNS record for domain jr.com)' (delivery attempts: 0)>



We can send email just fine....any ideas????
sbalawajderAsked:
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abhaighConnect With a Mentor Commented:
Then I would start checking the logs on the firewall and for AVG
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abhaighCommented:
sounds like someone has their reverse dns screwed up at their end and your system is trying to verify the source domain, failing, and then dropping the email and generating an NDR
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sbalawajderAuthor Commented:
I used mxtoolbox to do mxlookups on pretty much all of the domains trying to email us, and everything looks fine (as well as from my end)
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abhaighCommented:
'jripqe1.jr.local' is interesting - that, to me, is their internal DNS namespace leaking out - and certainly would generate an error at your end.

I'd crank up logging on the virtual SMTP server as well as the MSExchange Transport/SMTP protocol to see if you can capture anything more explanatory
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sbalawajderAuthor Commented:
Well, the "bounce" happens when they send it, as if it never comes here (I just looked through the logs this morning)...so im not sure exactly whats going on
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abhaighCommented:
what are you running for borderware?
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sbalawajderAuthor Commented:
borderware?
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abhaighCommented:
Spam filters, mime sweepers, etc...  processes that sit on the border between your exchange system and the outside world that filter traffic before it reaches Exchange
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sbalawajderAuthor Commented:
Our firewall (fortinet) acts as the spam filter.  We also have AVG Network Security installed that also acts as a spam blocker
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SurajCommented:
The NDR IS Cos you do not have a SPF Record created at the ISP.
CHECK if you have sender id filter  enabled? disable it. restart the smtp service.
try once again...
-x
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sbalawajderAuthor Commented:
Figured it out....of course it was my stupid firewall, grrrrrr

I had a check reverse DNS selected on there, I took that off and voila, no more bouncing
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