Error connecting to ActiveSync from BlackBerry Z10 device

Hello folks,

I'm hoping someone can help out as I'm at a bit of a loss here!

I get an error when trying to connect to ActiveSync using a BlackBerry Z10. I don't have another device I can test with yet.

"Service for account (email address) is not available. Contact your system administrator to regain access. [Error Code: 403]"

A BlackBerry KB mentions that it's an ActiveSync authentication issue: http://www.blackberry.com/btsc/KB33447

I checked the user's account in EMC as ActiveSync is indeed enabled.

Running the Get-CASMailbox cmdlet also shows the following:

ActiveSyncEnabled OWAEnabled           PopEnabled          ImapEnabled         MapiEnabled
----------------- ----------           ----------          -----------         -----------
True              True                 False               False               True

Basic authentication is also enabled on the CAS...

I also ran a test to our CAS array using a tool called ActiveSync Tester and get the following:

Thanks for any help you can provide