Recommend an email index tool for Emacs?

[Leo]

Dear all,

There seems to be a handful of email indexing tools out there. I have
not used any of them because I used to keep all emails on the server
and use its search engine.

Now I got a few thousands of emails on my harddisk. I tried grep once
and it is not very fast. Thus do you think an indexing tool is handy
and which one to go?

Thank you.

-- 
Leo <sdl.web AT gmail.com>                         (GPG Key: 9283AA3F)