PHlyMail
- A webmail client based on PHP and MySQL. Features include folders, multiple POP3 accounts, contacts, calendar, modular design to add new functions. It's multilingual and theme based. [Free and commercial versions]
- http://phlymail.de/

WapCoMail
- A friendly and easy wapmail interface to use your email from mobile devices. Developed in PHP 4 for Apache or Microsoft Internet Information Server (IIS). [Freeware]
- http://www.counterzone.ro

IMP
- Very popular IMAP webmail program. It relies on PHP3's IMAP module for the IMAP calls, and an SSL server for security. [GPL]
- http://www.horde.org/imp/

IlohaMail
- A light-weight multilingual webmail client with POP3 and IMAP support, written in pure PHP4. [GPL]
- http://ilohamail.org/

SocketMail
- A webmail system based on PHP and MySQL, designed for small-to-large web sites and enterprises [commercial].
- http://www.socketmail.com/

JAWmail
- Just Another Web mail is a flexible, powerful and fast webmail written in PHP [GPL].
- http://www.jawmail.org/

Squirrelmail
- A standards-based webmail package written in PHP4. It includes built-in pure PHP support for the IMAP and SMTP protocols, and all pages render in pure HTML 4.0 (with no Javascript) for maximum compatibility across browsers. [Free]
- http://www.squirrelmail.org/

HiveMail
- PHP system that allows one to offer personal email accounts to the site visitors. Complete customization, attachments support, and spam filters. [Commercial]
- http://www.hivemail.com/