Update: Blocking Unauthorized Devices from accessing OWA

With the help of several coworkers we are blocking the troublesome User-Agents.   Here is a way to do it:

ISAPI Rewrite is a Mod Rewrite implementation for IIS.   There is a lite and a full version available here:

http://www.isapirewrite.com/

So with the configuration below you can block the unauthorized blackberries.   I will edit the original post to include the solution.  For full details see the April 2008 post on the subject on this blog.

RewriteEngine  on
#Block Blackberry and other smartphones
RewriteCond %{HTTP:User-Agent}  (?:BWC.Worker.*|BWC.Engine.*|MSFT-SPhone.*|PalmOne-TreoAce.*|AvantGO.*) [NC]  
RewriteRule .? -  [F,L] 

Here is another approach for handling the blackberry devices which blocks it by IP address.

http://www.billwarnke.com/index.php/tech/38-internet/54-blocking-blackberry-bis-from-accessing-exchangeowa-email