Maintaining a whitelist

I have a problem maintaining a whitelist...

My DCC server is collecting checksums from a server acting as an UUCP relay
(no, UUCP is not dead). A few hundred domains have their MX pointing to the
UUCP server and download their mail with UUCP. This adds up to many
thousand users.

Maintaining a list of mailing lists these people are subscribing to is an
impossible task. Most mailing lists are very unlikely to have many
recipients here, but I am more concerned with auto responders off all
kinds.

I am interested in other peoples experiences with building whitelists.

-- 
Gustav Foseid, Initio IT-løsninger AS
gustavf@initio.no