PHP based POP mail reader
For the past few days I have been looking for a PHP based POP Mail Reader. Checked out a couple of them. I think that UebiMiau is a really good one. It is really easy to install and does not need any database. Also, it works great both on Unix/Linux and Windows. Really easy to configure.
PHP based IMAP mail reader
If you are looking for a PHP based IMAP mail reader, use SquirrelMail. It is definitely the best. I would not be searching for other mail readers if Squirrelmail supported POP. There is a workaround to read POP emails using Squirrelmail but you still need an IMAP server to store the data.