You will have to customize your own event sink; if you know some basic scripting use these resources. The first link shows how to detect an incoming message with an attachment; the second event sinks how to forward based on criteria.
How to register a transport event sink for the SMTP Service in Exchange 2000 Server
Journal per Domains or User
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I want to get an extra copy of incoming mails if they have some sort of special attachments. Let’s say if incoming email has an PDF or excel, I want a copy of email or attachment sent to some other account. Company is running GFI for both antivirus and spam and it is not capable of doing so. Exchange 2003 SP2
Any ideas? Appreciated