A useful feature for the anti-spam would be to allow the Spam whitelist to learn from outgoing emails (as outlook does) so that any emails which have been replied to or are from that person at a later date are not blocked.
Also, along the same lines but probably a little more complicated, It would be again useful to have the baysean spam filter to learn from the outgoing mails of users. This would then force the spam filters to almost immediately include the sort of emails which the users have replied to along with the general content being discussed by the users.
Thanks very much, it is a brilliant product so far.
Regards
Ian