We just rolled out a Blackberry Express Server, and would like to make sure that all Blackberry devices that our users own are connecting SOLELY through the BES server. We are running Exchange 2010 SP1.

I've read some links that discuss blocking BIS at the firewall level. Before doing that, however, I'd like to individually contact all users with Blackberries and make sure that they have a chance to switch to the BES server. I've sent a company-wide email, but unsurprisingly folks tend to tune these out until they are forced into action.

Is there an easy way to identify the users with Blackberries by searching IIS logs, or perhaps using the Exchange Management Shell? Especially some automated way? I've tried searching for the Blackberry identifier, but it does not appear next to any user name, so it's not as helpful as it could be.

Edit: to clarify, what I'm talking about is the fact that Blackberries can use OWA to download mail to the phone. We do not allow IMAP or POP access through our firewall so that's not a concern--just folks with Blackberries using Blackberry's hack to allow it to connect to Exchange without a BES server. As far as I know, Blackberries are the only popular phones that use this method to download mail.