Specify which e-mail domains or user accounts to allow or block when issuing licenses from this AD RMS cluster. To specify ...

Specify which e-mail domains or user accounts to allow or block when issuing 
licenses from this AD RMS cluster. To specify a user account, type the e-mail 
address ([email protected]). To specify all users in a domain, type the 
domain name (domain.com).  To specify all domains, type an asterisk (*).