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.
Atmail is a fully-featured email server and Webmail client, allowing users to send and receive email via a Web browser or mobile device. It has full support for IMAP mailboxes, and an optional email-server mode that uses EXIM as the MTA. Features include a scheduler, MySQL backend support, spell-check, address book, calendar user preferences, multiple accounts, SpamAssassin support, migration scripts from other mail servers, a customizable interface, an attractive AJAX interface, an optional group sharing Calendar/Addressbook, and an Outlook plugin to sync Contacts/Tasks/Calendar data between a Desktop, Mobile, and Webmail client or other email users.