ADJE WebMail is a set of Perl CGI scripts which provide a Web interface to existing email accounts on any POP3-compliant email server. The software provides a complete interface, including encoding/decoding attachments, email and URL markup in received emails, and an address book for each user.
Buni Meldware Communication Suite is an enterprise groupware product providing an email server, calendar server, and a Web mail client. The Web mail portion is written using Adobe's Flash and provides a rich cross-browser experience. Protocol support includes IMAP, POP, SMTP, iCAL, WCAP, and more. It uniquely supports full database email storage as well as file system storage of emails on major database platforms, and is easily installed via a Web Start graphical installation process.
phlyMail is a groupware, webmailer, and PIM. It offers unlimited nested groups, unlimited POP3/IMAP profiles, quotas, an integrated address book, a calendar with multiple reminders and event repetitions, a file manager with an integrated WebDAV server, the ability to send faxes, SMS support (which lets you send SMS, get reminded of events via SMS, and get email notification via SMS), a bookmark manager, themes, and multilingual support. It uses either sendmail or SMTP to send email, and can handle MIME and SSL connections. Support for IDN (Internationalized Domain Names) is included. Through its modular design, it's easy to add completely new features as modules, which can be plugged into the system.