Recently worked an issue where the question came up about the required attributes for an Exchange Mail-Enabled User object.  It took some digging through some documentation, but did manage to find some information on the topic.  I felt like placing this information into a single location to help guide those wanting to accomplish the task of creating a mail-enabled user object.

You will need three attributes to populate to make a mail-enabled user object.  These mandatory attributes are:

è mailNickName

è DisplayName

è TargetAddress

The Update-Recipient PowerShell CmdLet will be called based on how provisioning is setup in the Configure Extensions tab in the management agent properties, and providing the correct information in the Active Directory attributes.  You can find more information on the Update-Recipient PowerShell CmdLet by referring to the below links. 

è Exchange 2007

è Exchange 2010 SP1 Help

è Blog posting: Differences between Update-Recipient for Exchange 2007 and Exchange 2010

Community Resources

Exchange Provisioning using ILM 2007 and FIM 2010
Provision/Deprovision a Mail-Enabled User for Existing AD Users

See Also

Exchange 2010 Product Documentation
Create a Mail User
Configure Mail User Properties

Exchange 2007 Product Documentation
How to Create a New Mail-Enabled User