Group Email Style Plugin???

Hey guys …. I have been searching and searching for a way to do what I have in my head with existing plugins but have had zero luck. I searched for Yahoo Groups style plugins as I thought they would have most of the features but didnt have much luck.

So here is what Im looking for. I want to be able to post a form on the front end of the site that all registered users have access to. They then fill out the form and select a category (required) of which the request best fits in and when they hit submit it emails this request to all the users that subscribed to that category. So thats the front end.

Now the back end the user should be able to login and select which categories they would like to subscribe to so they are only getting emails of interest. They should be able to pick as many or as few as they want (it would be cool if the admin could limit the number, but this isnt a must have feature).

Basically I want to build a site thats a tool for dealers of a specific product to be able to mass email out to other dealers when they have a need for something, without revealing the email list. I hope this makes sense.