Exchange Server 2010 Queue is a mess...

I just obtained a new client today and the first issue they want me to work on is to determine why they can't receive external e-mail, but can send to external and send and receive to internal.  I setup a test account on their server and then sent the test account 4 e-mail from my server and sure enough they didn't go through.  I looked at the queues on my server and received the following error:  452 4.3.1 insufficient system resources (see screenshot below)

So then I opened the queue on their server and it is a mess; a ton of e-mails attempting to be delivered (see screenshot below).

I ran their domain through, and everything reports back ok:  no open relay, spf records, etc.  They are listed a few RBLs, but these are the extortion ones. (see screenshot).

I am at a loss as to what this could be.  Any help would be greatly appreciated.
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Can you run the exchange test here

Is autodiscover on?
YortAuthor Commented:
joinaunion - what test should I run (there are several listed)?  Yes, autodiscover is on.
On the exchange tab you can run,      
Microsoft Exchange ActiveSync Connectivity Tests
Microsoft Exchange Web Services Connectivity Tests

Run each test post back results.
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Nick RhodeIT DirectorCommented:
Is there MX record pointing correctly to the business address?  Do they have a static address for the business?  Do they have the ports open and forwarding to the exchange server on the router?
You can use MXtoolbox to check if the external MX or DNS records are resolving properly to the business:
Simon Butler (Sembee)ConsultantCommented:
How much disk space is on the drive that Exchange is installed on?
That is the primary reason for the failure you are seeing.

YortAuthor Commented:
Everyone...thank you all very much for your responses.  I will try to respond to everyone's suggestions.

First, the MX records, DNS, etc. are all setup correctly.  I confirmed all of this two times.   When I run the tests at everything comes back fine (I would post the results but they contain a lot of information I would rather not disclose and I don't have the time at the moment to scrub them).  The available disk space is 289GB.

My client's firewall is configured to only allow e-mail communication via port 25 from the explicit IP address of the internal Exchange server.  DNSstuff reveals that the Exchange server is not an open relay.  The next thing I looked at what possible password breaches...low and behold I think this is the issue.  After speaking with several employees and the management team, it turns out a lot of their passwords were something like:  password1234 (so a huge no-no).  I am now almost certain someone was connecting to the Exchange server using valid credentials via a hacked password to send spam.  We immediately setup a much more restrictive password policy and I implemented it last night.  After confirmation of all passwords being reset, I will reactivate the Exchange server and see what happens.
I don't think this is a password issue. Give this a read. I know it's exchange 2007,but it will get you in the direction.
Free Hard Disk drive space for the Message Queue Database
YortAuthor Commented:
joinaunion:  Again, thank you for your reply.  Our server is actually Exchange 2010.  The server doesn't meet any of the criteria for a back pressure issue.  Ample disk space, memory, etc.  The interesting thing is that within minutes of turning back on Microsoft Exchange Transport the queues begin to fill again with the same garbage as in my prior screenshot.  After a bit more reading, I am taking the following two actions:

  1.  Complete virus scan of the server, and
  2.  Activation of the Antispam feature, specifically configuring Recipient Filtering.

I will post back once the scan is complete and antispam is active.
YortAuthor Commented:
The issue turned out to be an improperly configured Receive Connector.  Once I isolated the bad connector, I corrected the settings and the spam stopped immediately.

Thank you to everyone for your assistance.

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YortAuthor Commented:
After further digging I found an improperly configured Receive Connector and fixed it.

Thank you to everyone for your comments and suggestions.
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