Mail List emulation

[JakeC]

I've had a request to set up a vB board that the users can decide whether they want to use it like a mail list or like a bulletin board. If they want to use it like a mail list, they should be able to indicated that durring registration and receive all posts via email and respond to posts using email as well. I've seen the hack that allows users to respond to postings from email but can I take it a step further to have certain user groups get every post through email and respond to them? Any ideas would be much appreciated.

JakeC