Just a quick tip for you out there and a reminder for me. If you are using .forward files with your MTA (so, real users, not virtuals) and you want to discard everything received by that user, just put in his/her .forward
"|cat > /dev/null"
Remember that the quotes, they are mandatory (if you’re copy’n’pasting this, change the quotes because WordPress loves to change things)
The eternal fight between admins and computers 
http://etbe.coker.com.au/2007/06/10/putting-html-codes-and-other-special-characters-into-a-blog-entry/
The above blog post has my solution to the quoting problem (a basic Perl script to replace with &#xx;), and the comments have some solutions that others use.
Just a “/dev/null” .forward, without the quotes is OK.