Help - need newgroup/mailing list type functionality

I have looked everywhere and checked into everything from Organic Groups (too complicated for my needs) to mailman (Bluehost only allows up to 100 subscribers - I have 650+).

Wish list:

**needs to be invisible, registered users can add their names to the mailing list when they register for the site and anytime afterward (mailman User register was awesome for this) - I'm at the point where I think I will have to manually do this.

**needs to allow any registered member to send an email out to the whole list (with admin approval, i.e. moderated mailing list), by simply sending an email to a specific email address "our-groups@thebestsite.com".

Thats it!