Modern user interface.
Complete support of IMAP and SMTP protocols including SSL and STARTTLS.
Minimalistic resources requirements.
Direct access to mail server is used (mails are not stored locally
on web server).
Allows for adding multiple accounts to primary one, simultaneous
access to different accounts in different browser tabs is supported.
Additional identities.
Administrative panel for configuring main options...

WWW: http://rainloop.net/