Free PHP Webmail With A Nice UI – RainLoop
RainLoop is a free and open source PHP webmail application for anyone willing to use a single interface for many accounts.
The application has a modern user interface and supports both SMTP + IMAP.
It doesn’t require a database as the e-mails are not stored by the app. The mail server is accessed directly and RainLoop simply displays the e-mails there.
Multiple accounts are supported and each inbox can be viewed in different tabs with no session conflicts.
RainLoop is capable of handling all major webmail functions and other handy features exist too (like Dropbox/Facebook/Twitter/Google integration, auto-completion of addresses or keyboard shortcuts).