Does anyone know how anti-virus scanners work for Outlook
messages?  Are they MAPI Spooler hooks?  Are they Winsock
LSP's?  If they are I certainly cannot find the hooks
they are making into my system.

I would like to understand the API level that they work
at.  In particular I am interested in outgoing messages,
but I would also like to understand incoming messages as
well.  

I am also wondering if there is any difference in how
these filters work for different versions of outlook and
windows.

Thanks for any pointers and assistance.