Hi Michael,
Thanks for your quick response. I was suspecting that I might need a backend IMAP server to run with RCM but wanted to make sure it was an absolute requirement. I suppose I should have noticed the word "client" in the description and that would have answered my question. lol
It seems that the server specs and bandwidth aren't going to be that much of a problem as we're going to be using a large datacenter and have plenty of servers setup in clusters. Finding a good, reliable IMAP server is going to be a problem it seems. I'll keep looking and, if anyone happens to have any recommendations, please feel free to forward them my way.
Thanks, Anthony
Just to throw my hat in here - we use OS X's Postfix/Cyrus mail server (or have for the past 3 years), and while it runs relatively smoothly, it's lack of configuration power can sometimes tie our hands and give us a grand headache. I'm not a strong supporter of it, and have looked for a more robust alternative - especially after fickle corruption from bootable backups, and other joys. The bleeding edge version may have some of these tweaked out, just noting.