adding Server side mail filters to Virtual Users And Domains With Postfix 7.10

[c0mputernick]

Has anyone added server side mail filters to their "Virtual Users And Domains With Postfix, Courier And MySQL Ubuntu 7.10" setup?

I would like to, but am unsure what to change in postfix/maildrop to be able to add this functionality. Can anyone assist me with this? Ive found some related gentoo material creating the file: /home/vmail/.mailfilter with this inside:
"
xfilter "/usr/bin/spamc"
# Check for user defined filter file
exception {
include "$HOME/mailfilters/$LOGNAME"
}
"
and then creating this file that holds the filters for this particular user:
/home/vmail/mailfilters/virtuser@somedomain.com

But i need to know how to change postfix to hand the mail off to maildrop instead of its normal delivery.

Any help would be much appreciated.