Mailing / distribution list

Hello,

I need a simple mailing list program/app/mod that works similar to meetup.com or Google Groups (not the google group module, doesn't do what I need).

Background:
I have a registration only community website, part of the main reason people sign up for the site is to get access to the mailing list. I have around 250 members and I get more everyday (this community was previously a Google group with over 650 members). The mailing list module is no longer working for me as I have too many subscribers and the server times out when trying to send out the message. I have all my users email addresses in my website user database.

My down to the nitty gritty need:
Lots of time I am on my cell phone etc and need the ability to just forward an emailed message I receive to the whole group. I've tried mailing list software dada mail etc. and I can't find a mailing list program that will do just this simple thing. Like with google groups there was a dedicated email address such as mailinglist@googlegroups.com that if you sent an email to that address it would sent it out to the whole group (depending on your moderation settings). Same thing with meetup its usually something like mygroup-meetup@meetup.com, any messages sent to this sends an email out to the whole group. I need to be able to do this desperately.

The mass contact module broke on me this week (too many users to handle it now), so I need a solution quickly. The community is private so I can't use something like Google Groups to power the mailing list as they would have to sign up for the mailing list separately and that will NOT work. The registration for the site is also assumed to be the registration for the mailing list.

HELP.
....my users are starting to get restless... :(

Thanks, email blocked in brooklyn