Hi,
I know that i'm asking a question that is probably proposed weekly to
this newsgroup, but I need some advice.

I'm part of an educational institution that provides mail adresses to
professors.
We are encountering regularly heavy performace problems with imap mail.
(we always use opensource tools)

Some teachers are used to keep all mails in one Gb size inbox file.
When they open their inbox, waiting time is extraordinary long and
performance hit is on disk i/o.
Even a cluster solution (that we are going to implement), could not
address efficiently this specific problem, because the disk i/o is
quite limited in nowadays technology (for low budget solutions)

I was wondering which tools would big companies like gmail use to
provide a fast service.
My guess is:
1. inbox file is split in multiple small files (this would improve
message seek inside the file)
2. header information are kept in a different format by ascii file.

This second point seems to me particularly important, as the inbox
opening is not cached by webmail software like squirrel and the process
of reading all the headers is very long.

I have seen different inbox formats like mbx and maildir, but i was
wondering if there is a real gain in performance. The drawback could be
the loss of tools like procmail.

I was wondering if it does exist a imap server that checks ascii inbox
files and creates a db of all headers. This db must be updated when
messages are receveid or deleted.But it could be used for header imap
commands.

Can anybody me?
Thanks,
Matteo Faleschini