A Better Open Source Webmail?

CandyMan writes: "Recently I have been forced to go back to a certain open source webmail (name withheld to protect the touchy), and I can't say I would recommend it to anyone. For emergencies maybe, but not for daily use. Lightning-quick full-text indexing and Javascript UI tricks in Gmail and Yahoo! mail have spoilt me forever, and I guess that most webmail users out there would feel the same. Old-style html-only webmail applications just don't cut it anymore. Which is your favourite webmail client? Is it a bare-bones html-only application, or does it have a fancier interface?"