Dear friends , i am facing this fromlem in my exchange 2010 for some users.
exchange sends a mail to users and says that you have sent spam mails out
i am giving the reply mail also.
To: Ganapati N.S
Subject: Returned mail: see transcript for details
Dear user firstname.lastname@example.org,
Your account has been used to send a large amount of spam messages during the recent week.
Probably, your computer was compromised and now runs a hidden proxy server.
Please follow the instructions in order to keep your computer safe.
The domainname.com team.
First go to www.mxtoolbox.com and check to see if you domain is blacklisted. Put your domain in the lookup box and click lookup. then click the BlackList link to see if you are listed. Then get yourself de-listed.
Second use your firewall to limit outbound emails to your mailservers only. If you don't know how to do this, post your firewall information here (make, model and code version if possible) and we'll see what we can do.
Third, turn on verbose logging on your receive connectors and then check to see where most of the connections are comming from.
Hope that helps.