Clasor InTouch is an ajax communication suite with key features such as webmail, address book, post-it notes, calendar (in progress), webdisk (in progress), built-in instant messenger and RSS reader. It is the first open source web application which features built in spam protection and instant messaging capabilities together with web 2.0 technologies.
It is built with Java, utilizes JSP/Servlets with the well known J2EE technologies & uses MySQL database.
Claros inTouch is more than a free webmail software with a slick interface & usability.
It is offered under GNU which makes this communication suite software totally free.