In a new tutorial from PHPMaster.com Jason Pasnikowski takes a look at sending emails with PHP - an introduction to what the language offers and how it can be used to send an HTML version.
In most cases your installation of PHP will be capable of sending emails. If you are using a shared host, or if you installed PHP using a package management system like apt-get, more than likely you're all set. You'll really only need to worry about extra configuration if you're compiling PHP from source or if you're running it on Windows. In either case, there are plenty of resources available online to help you out. Because that's all beyond the scope of this article, I'll assume you're set. If not, Google will be your friend.
He starts with a simple example using the mail function but quickly moves on to sending a multi-part email with an attached zip file and HTML content. He includes the all code you'll need and explains each part in detail so you'll know exactly what's going on.