I don't want to comment on the technology, but the idea of indexing
to me is the most interesting.
For a commercial client we are using Zimbra - and with one mail box
containing about 12 GB of mail I can search it for practically any
word, and even limit that to particular headers, or file types, or
content in a file (the list goes on) in sub-1-second. I also have
virtual mail folders that can use that same search and present those
folders as IMAP folders - very cool.
Now that is the killer app.
Mind you - Zimbra is just too big and slow - great for commercial
customers where you have maybe 200 or so email accounts on a box, but
I am sure we are more used to running systems with 10,000 users per
box - Zimbra would not cope (well... java...).
Scott