What are the requirements for mailing lists with PHP MySQL?

I have a few small time clients for my web-publishing side business. I would like to offer them email lists for newsletters and such. I want to know if it is possible to have the email address that is part of their domain send out mass emailings to those who have signed up. I have a basic understanding of PHP and MySQL. I think there is a way to do this, but I do not know. Ideally, they would be able to edit the content themselves and then the PHP and MySQL would take care of the HTML in the emails, and the server that hosts the site would actually send the emails, so that they do not need to do it from their computers.

I am currently using GoDaddy for all my server/domain/mail/database needs. Do I need anything I do not already have? I just need a simple explanation of where to start, and how all the various applications work together to create and send out the emails.

http://www.phpeveryday.com/articles/PHP-...

Read that instead of me explaining it on here. Just follow the tutorial, if you have an understanding of PHP and MySQL you should not have any problems.