Outbound mail filtering

[Gregory T Pelle]

What is the recommended setup for outbound spam filtering?

I would like to be able to have all of my web hosting machines route all
mail to a machine where the mail is virus scanned and spam checked.  I
would like to quarentine all mail that is considered spam (using Vipul's
Razor and maybe DCC).

I know I am not going to catch 100% of all spam, but I would like to
catch most.

I also plan on setting up firewall rules on the servers to block all
outbound smtp traffic unless it is going to my filtering server.

Any suggestions?  Am I missing something?

Greg.