Assume that the online archive feature is enabled for your Outlook account. You try to log on to Microsoft Outlook 2010, and then you receive an online archive credential dialog box. In this situation, the SMTP address is displayed incorrectly. For example, the address is displayed as GUID@DOMAIN.COM.
To resolve this issue, apply the following update:
2597011 Description of the Outlook 2010 hotfix package (x64 Outlook-x-none.msp; x86 Outlook-x-none.msp): December 13, 2011
Note If you create a new profile and then start Outlook 2010 for the first time, you may find that the user name is blank in the credential dialog box. To resolve this issue, use one of the following methods:
Close and then restart Outlook 2010.
Type your credentials in the dialog box.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.