You may find this utility useful: http://support.microsoft.com/support/kb/articles/Q274/7/10.ASP, but be sure that you have some real-time scanner working upstream of the Exchange box -- at the firewall level. If you find that Norton has not provided the solution you require, ask competing companies to help you clean-up. If they sense a potential sale is imminent, they should be more than happy to assist you. Why Norton's tech support has not assisted you yet, is a question to think seriously about.
Dig Deeper on Email and Messaging Threats-Information Security Threats
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