I would like to learn how to build a web-based email client in PHP (similar to yahoo and gmail).
Does anyone know how I can get started with this?
I would li
Set up an email account that can be accessed via POP (example: gmail). Then use the PHP IMAP functions to retrieve email via the POP protocol (POP is probably easier than IMAP) (http://us2.php.net/imap). For sending mail, use the PHP Mail functions (http://us2.php.net/mail).
If you're not using an external mail service (like Gmail) you will need to configure your own server to store and send email. Here is a tutorial for using Postfix (for sending mail) and Dovecot (for accessing mail via IMAP). This tutorial also explains setting up a webmail system in SquirrelMail. You could do this, or, if you really want to develop your own system you could write a PHP application to access your mail.
Good Luck!