I have a user who is receiving 1000+ undeliverable messages form mail servers all over the world. It appears that someone is spoofing hise-mail address. I have confirmed that none of the emails are originating from our mail server. Is there anything that we can do to stop this or will I need to change his email address?Thank you

Hello, May I know which kind of e-mail system that user is using? I would highly suggest that you post this in our Exchange forum, no matter whether it is related to Exchange Server. People there have better knowledge on email systems and they may have better ideas about how to prevent this. Besides, people there may share some useful information with you. http://forums.microsoft.com/TechNet/default.aspx?ForumGroupID=235&SiteID=17 Thank you for your understanding and cooperation. Best regards,Chang Yin