procmail as a content_filter with dovecot

I am using Mac OS X Server. OS X Server uses postfix with dovecot set as mail_transport.

I want to add procmail to the mix. I cannot use the (typical) mailbox_command = procmail -a "$EXTENSION"

because mailbox_transport = dovecot

overrides any mailbox_command parameter and it is NOT Possible to change, remove, or otherwise vary the mailbox_transport on OS X server.

I'm thinking I should be able to set up a content_filter for procmail, but I've found nothing online to tell me if this is possible or how to declare it.

Can anyone help?

-- Vicki cfcl.com/vlb twitter.com/vlb