Exchanger server spam

Exchange server, Windows SBS 2008, is sending spam email internally.  It is sending emails from bogus email account that don't exist on our network.  We have Baracuda Spam Firewall and a smart host.  I checked our smart host to see if they are sending out externally, but they are not, just internally.  How do I find out what account has been compromised?  Thanks.
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TlingitAsked:
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R--RCommented:
Enable the SMTP log on Exchange server and check the IP which is sending maximum hit in the SMTP log.
Once you find the IP disconnect the PC from the network.
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ash007Commented:
Hi,

As you are receiving spam from internal domains its called Spoofing so need to set permission on receive connectors

Use the following command to remove the ms-exch-smtp-accept-authoritative-domain-sender permission from NT Authority\Anonymous Logon on internet-facing Receive Connector(s):

Get-ReceiveConnector “My Internet ReceiveConnector” | Get-ADPermission -user “NT AUTHORITY\Anonymous Logon” | where {$_.ExtendedRights -like “ms-exch-smtp-accept-authoritative-domain-sender”} | Remove-ADPermission


http://exchangepedia.com/2008/09/how-to-prevent-annoying-spam-from-your-own-domain.html
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TlingitAuthor Commented:
Thanks for the information.
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