Exchange emails problem, nothing in,nothing out ?

One of the 2003 Exchange server is having some problems today, since 11am this morning, no external emails , and sending out also affected as no one external gets them, no errors on the server from the Event Viewer, and nothing showing in the queue, internal emails all working ok, but can anyone shine some light on this one ?
I know one of the workstation is infected and listed on CBL since early this morning, but this shouldn't affect incoming ?
Thanks for any help on this one, I am totally lost as to why ?
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Mahesh SharmaCommented:
If both sending & receiving public IP's are same & black listed right now??
Please check

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CombemartinAuthor Commented:
Just an update, I restarted the server and incoming seem to be working, but I really would love to find out what caused this pain.
CombemartinAuthor Commented:
Is there a good cheap or free and simple software to monitor the traffics on the LAN, hopefully can be useful to track any machines that may be spamming outside the normal Exchange ?
Mahesh SharmaCommented:
If it's related to server then check event logs. It may be related to some service only
Look through your eventlogs, since a reboot of the server corrected issue, I am guessing that one of the services for exchange crashed, probably the smtp service as internal will still work. an Error 7031 has a hot fix avail check this url:
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