Almost a year ago, I discovered a very promising open source webmail application called
RoundCube : not only does it use some ajax, but it’s fully skinnable via XHTML/CSS2 which is a huge plus when you need customizing for clients. The downside (sort of) is that it’s only IMAP right now.
RoundCube Webmail is a browser-based multilingual IMAP client with an application-like user interface. It provides full functionality you expect from an e-mail client, including MIME support, address book, folder manipulation, message searching and spell checking. RoundCube Webmail is written in PHP and requires the MySQL database. The user interface is fully skinnable using XHTML and CSS 2.
Anyway, when you’ve used sqWebmail, Horde or squirrelMail, you just wonder why the hell the interface is so ugly. It’s like being back in the 90s... RoundCube provides a nice alternative, and the current beta is fairly stable and usable in production. I have it installed on my dedicated server and feedback from clients is excellent
Some stuff is not totally ironed out still, Mac FF has some refresh problems (but Safari works *great*), but other than that everything is fine.
Thought I would share...