That feature has been available for several years :-)
Please see the relevant section of our manual:

Starting from SpamFilter ISP v 2.1, when an end user forces the delivery of a quarantined email to his mailbox, the sender of that email will be whitelisted so that the number of false-positives (good emails wrongly classified as spam) is reduced. The list of user-created entries is stored in the file AutoWhiteListForceDelivery.txt. The whitelisting is on a per-user basis, meaning that a sender is whitelisted only when he sends emails to that specific recipient. This will prevent a user mistakenly whitelisting a spammer, who could then send spam to all of your users.

We automatically whitelist our users outgoing recipients, but had to write our own mail log parser. MS's Logparser is perfect for this and its free. We parse the mail outgoing server log file every 10 minutes and script the creation of "FROM|TO" pairs in the db. We also added a date field to the tbl_autowhitelistdelivery table  and when we parse the mail log we update the date in the table if it already exists. Once every six months we run a procedure that deletes autowhitelistdelivery table entries that have not been emailed to in 6 months. This helps keep the db to a reasonable level.

Edited by WebGuyz - 07 May 2008 at 12:07am

Webguyz,  would you mind sharing?  If so, PM me or jerbo128   - hotmail

Thanks