You enable Microsoft Exchange Server 2010 Service Pack 1 (SP1) Password Reset Tool on an Exchange server that is running the Client Access Server (CAS) role. Now, Outlook Web Access (OWA) enables you to change your expired password, or the password when you first log on to OWA. However, you cannot change the password if the user name that you type in OWA is in user principal name (UPN) format.
To resolve this issue, install the following update rollup:
2529939 Description of Update Rollup 3 for Exchange Server 2010 Service Pack 1
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.