Are you using the Mogul's built in Messaging app for your IMAP mail? I did the same thing and it took forever, just like it does for you. However I got FlexMail 2007 and it's much faster. It's really a better e-mail application all around than the OEM app. If you don't mind spending the cash on it, I highly recommend it.
http://www.pocketinformant.com/produ...id=mail&dir=wm