Emailing list

I want to have a members only area of my site and only give access to people that subscribe to my newsletter. I can do this easily enough by protecting the directory and adding users manually to it, bit I’d like to find a way to add the user and assign the password automatically and generate at email back to the users email telling them their login info. Is there a 3rd party tool that can accomplish this? So I want a user to fill out a web form, have that automatically add them to my mailing list as well as give them access to my members only directory, and generate an email back to them with the login credentials. Of course, I would want them removed if they opt out.

My newsletter management software can’t do this, and I haven’t found one that can.