Normally I use ConstantContact for mailing list type things. However, this is a software in which you need to have the e-mail addresses and is not for sending things such as "E-Mail blasts". I've used it recently and a couple times before, I'm very pleased with the service and the support. Check it out http://www.constantcontact.com/index.jsp.
Most hosting accounts should include this. You shouldn't pay extra for this sort of thing.
The OP probably wants someone who specializes in bulk emailing rather than use
a script and possibly get his host IP banned. The providers I mentioned above do
work hard to ensure email delivery and maintain relationships with ISPs and any