There have been some step by step tutorials to do this on the forum... The only other option you can look into is a 3rd BES/Exchange provider which is what alot of us, whos company do not proice this do. for 17. 98 with a forum discount I get all the beneifts of exchange, and a BES.
www.exchangemymail.com can answer any questions you have about this method, as well as offering a 10% discount on your service since you are a BBForums member. Basically you forward your email to your EMM service, and they set up a reply to address. You also get the benefirts of wireless synchronization of calendar, tasks, notes, MDS (no charges from cingular outside your BB UNLM plan, for use of 3rd party software) etc.