On the Techfounder blog (from Eran Galperin) there's a quick tutorial about using the Zend_Mail component of the Zend Framework to send both normal, plain-text emails and ones with MIME attachments.

Using PHP's built in function (aptly named mail() ) is relatively straightforward - until you need slightly more advanced features, such as adding and encoding email headers or sending multiple mails efficiently. Fortunately, the Zend Framework comes with a very capable mail component called Zend_Mail.

He shows how to send a simple email, do something a bit more complex with a custom SMTP server, read messages from a remote POP3 email box and how to attach a binary file/message.

On the PHPClasses.org website there's a new entry covering, among other things, one handy feature PHP includes to let developers read and write their data more flexibly - streams.

This article explains what are stream handlers and how they simplify PHP developers lives by allowing PHP applications to easily read and write data from containers, like remote Web pages or e-mail messages, as if they were files. [...] The article also presents more examples of cool stream handlers classes submitted to the PHPClasses site by several authors.

He describes the abstraction that the streams interface allows, how they can make your life easier, a real-life example of streams in action (working with POP3) and some of the classes that have been contributed to PHPClasses.org that use them.

PHPit.net offers up yet another fine tutorial for your learning pleasure - this time with a focus on email, reading it that is in Read your e-mail with PHP (catchy, eh?).

E-mail is something we use every day, and almost everyone has their own e-mail address. To read our e-mail most of us tend to use something like Microsoft Outlook or Mozilla Thunderbird, but it's also possible to use PHP to read your e-mail. In this tutorial you will learn how.

I will take you through all the steps necessary to read your e-mail with PHP, and show you how to display all the newest e-mails in your inbox.

They use the POP3 class from PHPClasses.org to do most of the work, from connecting to thse server, logging in, grabing stats (like the number of emails), and grabbing and parsing out each email's data.