Ah yes, I understand that it'd be a Bad Thing(tm) to email all the board users. That's why I was looking for a hack that just emailed a selected usergroup -it's not going to be more than 40 people, and the traffic on the subforum should only be 3 or 4 posts a week.
Currently a single person is allowed to post to the forum and then she has to email all the people who might be interested. We need to do it like this so no one can say "I wasn't told about it"