Last year when we released Exchange 2010 SP1, we posted about the change expired password feature in Outlook Web App and how you can enable it by creating the ChangeExpiredPasswordEnabled registry entry. See So you want to change your expired passwords in OWA... for details.
Since then you've sent us many requests for supporting the use of User Principal Name (UPN) format in the same feature. Previously only domain\username format was supported when entering domain credentials.
We passed on that feedback to Exchange PMs and we're glad to let you know that the support for UPN credentials is now available in Exchange 2010 SP1 RU3-V3, which was released recently.
Read out at http://blogs.technet.com/b/exchange/archive/2011/07/11/exchange-2010-support-for-upn-credentials-in-owa-change-password-feature.aspx
Read my favorites blogs:
Designing a backup less Exchange 2010 Architecture
Step by step guide for upgrading Active Directory from Microsoft Windows 2003 to Microsoft Windows Server 2008
Microsoft Exchange 2010 CAS Array – Steps and Recommendations
Appear Offline in Microsoft Office Communicator Server 2007
Microsoft Exchange 2010 Test cases