Even with the improvements to spam handling, it could still take a while to send out several campus wide e-mails. Since e-mail is one of the methods the college relies on to send emergency notifications this is a problem.

The most common bottleneck in mail servers is disk I/O. Our servers were not an exception, so we set out to elliminate that problem and have a system which was scalable so that if we needed more performance in the future we could add another server to the pool.

Our first step was to evaluate our IMAP server software and determine whether switching software or mailbox formats would decrease the load put on the disks. After doing quite a bit of research and setting up several test environments we found that by switching to dovecot we could decrease the amount of disk io by an order of magnitude. Dovecot does this primarily by keeping indexes of e-mail headers. Even on our old server we dramatically increased performance just from switching from UW-IMAP to dovecot.