Exchange 2010 Emergency - inbound external mail has stopped

Reaching out.

Our exchange 2010 server has worked flawlessly for a year now.  Today all of a sudden we are no longer receiving inbound external email.
Note - internal mail works both ways!

Environment

2008 R1 server running in a VM on ESXI 4.1 platform
2010 Exchange Server

I have verified that we can telnet to both ports 110 and 25 to our server
There are no errors in the event viewer
All exchange services are running
We have rebooted the domain controller running exchange no change
We are using an external GMAIL account to test.  NOTE - no kick back??

Please help!! thanks
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j-teksolutionsAsked:
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
if you manuall poke an email into the SMTP server, does it get delivered to the receipient?
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j-teksolutionsAuthor Commented:
What is the procedure to manually do this?  Thanks so much for your quick response
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
just quickly test with this

http://www.mxtoolbox.com/diagnostic.aspx
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
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j-teksolutionsAuthor Commented:
Great tools running these tests now
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TheGeezer2010Commented:
If this is inbound mail you will need to be able to access your port 25 from EXTERNALLY, telnet to it internally will only tell you the port is open, not that it is accessible from external.

Please plug either your IP or Domain into this tool and test to confirm that you are accessible from external locations :-

Go here first and find out the FQDNs for your MX Records :-

http://centralops.net/co/

On each of these FQDNs, plug it into here and run a test :-

http://www.test-smtp.com/

You will see real-time if you are accessible externally

HTH
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j-teksolutionsAuthor Commented:
So far one item of concern.  Reverse DNS failure?   Everything else is passing
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Well reverse DNS failure, will always have been there.

But did you getvan email?
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Reverse DNS is used by most mail servers to check its a valid mail server on outbound mail.
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j-teksolutionsAuthor Commented:
Resolving hostname...
Connecting...SMTP -> FROM SERVER:
220 dc.ourdomain.local Microsoft ESMTP MAIL Service ready at Thu, 22 Mar 2012 11:13:46 -0400
SMTP -> FROM SERVER:
250-dc.ourdomain.local Hello [184.72.226.23]
250-SIZE
250-PIPELINING
250-DSN
250-ENHANCEDSTATUSCODES
250-STARTTLS
250-AUTH
250-8BITMIME
250-BINARYMIME
250 CHUNKING
MAIL FROM: test@test.com
SMTP -> FROM SERVER:
SMTP -> ERROR: MAIL not accepted from server:
RCPT TO: myinternalmail@ourdomain.com
SMTP -> FROM SERVER:
452 4.3.1 Insufficient system resources
SMTP -> ERROR: RCPT not accepted from server: 452 4.3.1 Insufficient system resources

Message sending failed.
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j-teksolutionsAuthor Commented:
just had modify our domain etc for security of course
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j-teksolutionsAuthor Commented:
BTW with the wormly test i did get the test email
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
okay, so if mail server accepted test email from wormly to mailbox, exchange server mailflow must be working, so issue is beyond your mail server, possibly?
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j-teksolutionsAuthor Commented:
We figured it out.  After looking up that 452 error, we checked the hard disk space on the server and found we were under 4 gigs available.  Mail is flowing again after freeing up space.

Thanks for the quick replies!
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Im surprised you received the test email?

unless you freed up space before test?
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j-teksolutionsAuthor Commented:
The wormly test allowed us to specify two internal email addresses.  I was able to telnet to the smtp server and send emails between addresses on our local domain the entire time.  Only when an email originated from an external domain, was it being blocked.

 I would have assumed that all mail would stop being delivered once the disk was full, but that does not seem to be the case.
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TheGeezer2010Commented:
Glad you have it fixed.

If you have this disk space left, the problem could well have been either insufficient temp space, or even page file. Hope my advise assisted you in finding the solution.
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j-teksolutionsAuthor Commented:
Space issue thanks Hanccocka for your help!
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