Simple, modern & fast web-based email client

 Rainloop is a PHP-based MUA with a modern interface and no database
 requirements.
 .
 It supports IMAP and SMTP protocols (including SSL), Sieve scripts, multiple
 accounts and identities, an admin panel for configuration, and integration
 with a variety of commonly-used services. Plugins can be installed to further
 extend functionality. Emails are not stored locally, but are accessed through
 IMAP.