I recently gave Dovecot a try.
It's not nearly as featureful (or seemingly as stable) as
courier-imap, but it has one very important distinction:
It is *wicked* fast.
It made me think - indexes are what makes dovecot so fast. What would
it take to add similar indexing capabilities to courier-imap?
So, if you want to evaluate indexing you need to take a reasonably
popular IMAP client, log its IMAP commands, then show how indexing
will help. Arbitrary benchmarks won't cut it, and adding indexes for
the benefit of a lesser-used IMAP tool will come at the expense of
greater overhead for the rest of the IMAP clients, which makes no sense.
I can't speak for him, but perhaps he's referring to server-side
And how would the server telepathically know what the client is going to
search for, and thus prepare a suitable index in advance?