How can I configure Active Directory to enable SharePoint users to authenticate with [email protected] rather than domain\username?
I have done this before and by adding an item to the select box found in '[username] Proeprties' > 'Account' > 'User login name' but I cannot remember how to do this.
If you're not after the syntax username@domain and really want to have [email protected] you need to set this UPN explicitly and that differs from the SAM account name. This means that you can add a real e-mail address as login username for an AD-account.
You can also explicitly configure a user account to have a UPN whose username component is different from the SAM Account Name and whose domain component is different from the name of the domain.
The Account tab in Active Directory Users and Computers shows the UPN under the heading "User logon name" and the SAM Account Name under the heading "User logon name (pre-Windows 2000)". So if you are having trouble with particular users I would check that there aren't any discrepancies between these two values.
Reference: Any difference between DOMAIN\username and [email protected]?
As @BennySkogberg mentioned, you need to specify a UPN explicitly for the users you want to change. You will probably want to setup the Forest or Organisational Unit (tenanted) with a UPN Suffix. Once you have set the suffix, you should be able to select it under the user's Account name.
You can use ADSI Edit to modify the uPN Suffix property, or use 'Active Directory Domains & Trusts' as per the KB article below.
The following pages will have more information on this: http://jorgequestforknowledge.wordpress.com/2010/10/12/user-principal-names-in-ad-part-2/ or the KB for Setting the UPN Suffix for a Forest: http://support.microsoft.com/kb/243629
