Roundcube

RoundCube Webmail is a browser-based multilingual IMAP client with an application-like user interface. It provides full functionality you expect from an email client, including MIME support, address book, folder manipulation, message searching and spell checking.

http://www.roundcube.net/

Plugins

• http://trac.roundcube.net/wiki/Plugin_Repository
  
• http://plugins.roundcube.net/
  

Login via Basic Auth

https://github.com/roundcube/roundcubemail/tree/master/plugins/http_authentication

Serverinfo

http://axel.sjostedt.no/misc/dev/roundcube/

ManageSieve

https://github.com/roundcube/roundcubemail/tree/master/plugins/managesieve

VBoxADM

https://github.com/gittex/roundcube-plugin-vboxadm