I struggled with this one for a while. My old Instinct would allow me to get Exchange mail to the Sprint Mail Client on the Instinct via OWA credentials. Of course, it did not originally work when I got the Instinct. It was not until they came out with an update to the mail client, but once they did that it worked slick. Now trying to get my BlackBerry Curve 8330 setup to do the same thing was initially frustrating as well. Attempting a number of different things and then finally broke down and called Sprint. They basically said that it was not possible without getting with the Exchange team at work. I didn't have to do that before. It sounded as though it would only work with BlackBerry Enterprise Server (BES), but I only had BlackBerry Internet Service (BIS), as it is a personal phone, etc.
Anyway after much searching I found the document that I needed to get it done. It was a BlackBerry KnowledgeBase document. KB03133 to be exact. I had read posts telling you to find the CN name, post telling you to find out your mailbox name and use it, etc. Well it was this KB document that gave me what I needed. I had all of the info, except for what truly needed to go into the mailbox name field. It may not be as difficult for many, but as my work e-mail account has changed many times, I think that made it a bit more difficult. The big point of the KB is to login to your e-mail account via OWA and then hover over the Inbox or one of the other items in the navbar area and look at the lower left hand corner of your browser. What you need for your mailbox name is what displays in the address bar after the last slash in the address and before the pound (#) sign. My cn name was firstname_first-initial-of-lastname, my mailbox showed lastname, firstname. It was here when looking at the address that it showed something different than all of the Outlook configuration information. It showed firstname_lastname, which was different than it displayed anywhere else (so use what is shows for you, not just firstname_lastname as mine happened to show). My e-mail address is firstname.lastname@example.org. So once I had this little tidbit to put in, bingo, I was able to receive my e-mail from Exchange. No BES, no additional cost (I already have an unlimited data plan), no additional software on my PC desktop, etc. Of course, this only gets you the mail from that point forward, it does not download what is already in the box. It also does not pick up the Calendar info as the Instinct mail client did. This can evidently be done via BES, but I can live with just getting my mail, at least for now.