When you try to configure Outlook by Online Service Single Sign In application, you receive the following error message:
Outlook cannot be configured in the Single Sign In application.
The issue may be result from the dis-match of user principal name (UPN) and the Default SMTP Address. If they do not match, Microsoft Online Single Sign In application cannot complete the configuration of Outlook. To make sure that the UPN and the Default SMTP Address match, follow these steps:
a. Sign in to the Microsoft Online Administration Console.
b. Under Actions, click View User List.
c. In the All enabled users list, click a user's display name.
d. In the Edit User box, compare the text in the User Name and Domain boxes to the default address in the Alternate E-Mail Addresses box, and make sure that they are the same.
If you have other questions on this issue, please open a post for discussion in BPOS forum or contact Microsoft Support to ask for help.