Only which I miss at Roundcube which 6zap offer am the calendar otherwise please me Roundcube substantially better.
Also there are those for roundcube many extensions nearly all needs now already takes off.
SquirrelMail or also horde are only as I mean genuine alternative whereby SquirrelMail simply by the multiplicity of Plugins convinced, I think however in one year see already completely differently out one see so already that the RoundCube Community constantly grow.
I tried so far many WebMailer out and give it for me no more comfortable and better Webmailer such as RoundCube. Cleanly programmed constantly is developed further and maintained the Community is also class and before all which I finds particularly good which one the development whether over dev list or svn trac also constantly pursue can.