FastMail's Email Search Architecture
If you want Xapian search on a local maildir, I highly recommend notmuch[1]. Adding new mail and updating the index can take noticable time, but searching is super fast, it allows easy custom tagging, and search results are better than gmail in my experience.<p>I use it from the emacs notmuch mode.<p>[1] <a href="http://notmuchmail.org/" rel="nofollow">http://notmuchmail.org/</a>