In the below example we will add the UPN (User Principle Name) to a Contact so it can be matched to in the Directory Connector
For more detailed information and some screen shots, see attached document
Dell Software does not provide support for problems that arise from improper modification of objects using the Active Directory Schema MMC. Warning: If you use the Active Directory Schema snap-in, and you incorrectly modify the attributes of Active Directory objects, you can cause serious problems. These problems may require you to reinstall both Windows and Exchange. Microsoft cannot guarantee that problems that occur if you incorrectly modify Active Directory object attributes can be solved. Modify these attributes at your own risk.