Exchange 2010 stope receiving external mail

ecubenetworks used Ask the Experts™
I recently setup an Exchange 2010 in an Exchange 2007 environment.  All user (minus test accounts) reside on old 2007 server.  OWA and mx record both point to new 2010 server.  THis worked great for about 3 weeks.  Now every other day, we are unable to receive external email.  Once I reboot new Exchange 2010 server, mail flow works fine....for a couple days.  Then it stops again.  I cannot find anything in the event logs.  Any ideas?
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Next time it stops go to and select inbound smtp. Enter your server details and check the results.

Its a free microsoft service.

Another thing that springs to mind, backpressure, exchange 2007 and 2010 have a feature built in that monitors the disk usage and if the disk space drops on the drive that holds the installion of the hub transport role it stops working.

Hope this helps


I have run the  test when it occurs.  It says that the connection was refused.  

There is 27GB of free space on the c drive and 449 gb free on d:.

Another piece that I left out is that our mail goes to Trendmicro for SPAM.  But I do not think the issue is on their side because the reboot fixes it.

when you stop receiving mails, have you checked all the services?
are people still able to login to OWA and such?
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Ok, is it a typical exchange installation? Ie, is the CAS, HUB and mailbox role installed on the same server?

Can you telnet the server when it happens? Do you reveive any specific NDR's?


Checked services and all are running.  No errors in event log.

Did not try to telnet, but here is the message that external senders get when trying to send mail to my server:

Your message could not be delivered for more than 2 hour(s).
It will be retried until it is 5 day(s) old.
For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can delete your own text from the attached returned message.

                   The mail system

<>: connect to
    Connection refused
Is the trendmicro a hosted solution? Or is it installed on your server?
could it be that your resources are fully loaded on the server? (ram etc)


Trendmicro is a hosted solution.

Server is barely using anything (1% CPU and 1.65GB of 8GB of Mem).  All it is doing right now is incoming mail.  I have not migrated user mailboxes yet.
can you find event logs in the 2007 server?
can you try and move 1 mailbox to 2010 or create new one there, and see if that mbox experiences the issue as well?
Have you got any test mailboxes on the new server?

Can you send an external email to that mailbox? When it happens

Could it be an internal routing issue? I assume you have correct dns otherwise it wouldnt work.


No...I tried that.  All external mail is rejected.  I have 6 test accounts on new server.  Could not send to any of them.  Some of the test mailboxes were migrated, and some were new.  None could receive external mail.
i would try and telnet and deliver mail to the server that way, then check to see what this tells you.


I am seeing the following errors all over the 2007 Exchange event viewer:

Microsoft Exchange could not find a certificate that contains the domain name in the personal store on the local computer. Therefore, it is unable to support the STARTTLS SMTP verb for the connector scanner with a FQDN parameter of If the connector's FQDN is not specified, the computer's FQDN is used. Verify the connector configuration and the installed certificates to make sure that there is a certificate with a domain name for that FQDN. If this certificate exists, run Enable-ExchangeCertificate -Services SMTP to make sure that the Microsoft Exchange Transport service has access to the certificate key.

For more information, see Help and Support Center at
this can be easily ingnored, it means that you have specified to use as SMTP banner, but don't have the certificate to match.
this is not related

try to send a mail over telnet, this will give us more clues in what's happening


how do u send a mail over telent?


It just happened again today. Tried restarting all Exchange services twice...No luck.  Had to do 2 reboots to get it back up.  Nothing in event viewer.  Here is the report from ExchangeServerTest :

 Testing Mail Exchanger
  One or more SMTP tests failed for this Mail Exchanger.
   Test Steps
   Attempting to resolve the host name in DNS.
  The host name resolved successfully.
   Additional Details
  IP addresses returned:
 Testing TCP port 25 on host to ensure it's listening and open.
  The specified port is either blocked, not listening, or not producing the expected response.
   Tell me more about this issue and how to resolve it
   Additional Details
  A network error occurred while communicating with the remote host.
When ot runs open exchange management shell and run test-systemhealth

Is there any red?


no red...just some yellow warnings about network drivers being more than 2 years old.  FYI- I have no other network issues when this smtp trouble occurs
OK...I think I have narrowed the issue down to the NIC cards.  I have two teamed Broadcom NetExtreme II cards (in a Hyper V  environment).  When this issue occurded last, I disabled the NICS and re-enabled them.  External email immediately started working again.  I am going to upgrade drivers and see if this resolves the issue.


Upgrading NIC drives resolved issue.

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