Copying Email from Server to Server via IMAP with Mail Carbon

I stumbled upon Mail Carbon the other day, a great little open source app @ sourceforge (http://mailcarbon.calfater.com/) that allows you to specify 2 IMAP servers & the user's account information, which then transfers all of the email from the old to the new, maintaining hierarchy (folders) and all of the good stuff that we get out of IMAP.

You can also use this app to simply backup all of your IMAP email quickly and easily, but the great benefit comes to webmasters that find it difficult when client's need a new host and have to go through the tedious process of getting them to backup their email before the switch.