Mass emails going out from postmaster account

It seems that i am sending out massive amounts of spam on my SBS2003 server.  The spam sender seems to be from postmaster@"mydomain".com or and the recipients are all different.

How I found out that I had a problem: I have a dynamic Ip address so I use a mail relay service from that allows me to send email.  Tzo has a cap on the amount of emails that I can send (2000) per month.  Tzo notified me that I had exceeded that amount already this month.  So, I am monitoring the connector queue in Exchange that forwards my mail to Tzo and that I see the postmaster@"mydomain".com or emails being submitted to the queue.

I have disabled my outgoing mail on exchange.  I noticed a folder called masssender in c:\program files\ which I deleted. I am still generating emails.  HELP !  Thanks
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A stack of outbound mail as postmaster@ is more likely going to be NDR spam - you would need to enable recipient filtering and tarpitting to resolve that (but it isn't going to work if you are using the POP3 connector)

masssender.exe looks like it could be legitimate for sending mail, but it could also be a very agressive hack (as opposed to a simple trojan)

Changing passwords/doing full rootkit and virus scans would be a good idea right about now.


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