We use a setup as seen on http://grab.by/agCb for about 30.000 simultaneous(!) imap connections.
We have 2 Foundry loadbalancers. They check the health of the directors. We have 3 directors, and each one runs Brandon's poolmon script (https://github.com/brandond/poolmon). This script removes real servers out of the director pool. The dovecot imap servers are monitored with nagios just to tell us when they're down. This setup has been absolutely rock solid for us. I have not touched the whole system since november and we have not seen any more corruption of meta data, which is the whole reason for the directors. Kudos to Timo for fixing this difficult problem. Cor
