Not that I am aware of... the only alternative approaches that I know of are

a) Redemption

b) CDO

I generally adopted CDO myself but obviously that requires having access to certain bits of info - ie smtpserver etc...

I suspect you have the page bookmarked already Ron de Bruin's page covers both of the above (and clickyes):

http://www.rondebruin.nl/mail/prevent.htm

(I think anything else would be considered circumventing security....)

The security warning came in with one of the SPs on 2000 I *think* ...