Someone else asked about this a while back, I don't think it can be done without modifying one of the vb files, since there is a hard-coded query to find users who haven't visited since the last notice was sent out. And I should mention that I think a bigger problem for some forum owners, other than spamming people's mailboxes, is that if you had a busy thread with lots of people subscribed, you could be sending out a very large number of emails (this may or may not be a problem for you).