If the user is part of any AdminSDHolder group they will lose the send as permission.
Here is the complete list of AdminSDHolder Groups:
xxx8226; Enterprise Admins
xxx8226; Schema Admins
xxx8226; Domain Admins
xxx8226; Administrators
xxx8226; Domain Controllers
xxx8226; Cert Publishers
xxx8226; Backup Operators
xxx8226; Replicator Server Operators
xxx8226; Account Operators
xxx8226; Print Operators
If he is part of any of the ones above the best way to fix it is to a) remove the user from the group or b) run the dsacls script from
The xxx34;Send Asxxx34; right is removed from a user object after you configure the xxx34;Send Asxxx34; right in the Active Directory Users and Computers snap-in in Exchange Server