Hastymail is a full featured IMAP/SMTP client written in PHP. The goal is a full featured yet lightweight Web mail client. After a complete review and rewrite, it provides many improvements over the original code including optional AJAX functionality, improved code organization, a plugin API, CSS and PHP template themes, and much more.
NOCC is a simple and fast Web-based e-mail reader which can handle POP3, SMTP, and IMAP servers. It is written with PHP5, and uses sessions, has low requirements (no database, frames), and is easy to install. It also features multi-language support, MIME attachment decoding/encoding, and the ability to display HTML messages.
EMEXIS WEBMAIL is a Webmail application based on SquirrelMail. SquirrelMail client is a complete Webmail system, but due to the concern of making it compatible with many browsers and systems, its interface has become a little impaired. EMEXIS WEBMAIL was developed with the intention of solving this deficiency. It comes with all functionality of the original Squirelmail, but with an interface that is much more friendly for the user. It mostly uses the mechanisms for handling messages from Squirrelmail.
Inbucket is an email testing service. It accepts messages for any email address and makes them available to view via a Web interface. It allows Web developers, software engineers, and system administrators to quickly see the emailed output of their applications. No per-account setup is required. Mailboxes are created on the fly as mail is received for them, and no password is required to browse the content of the mailboxes.