The ACL property of an attribute determines what permissions a user needs to modify the attribute. The ACL property value definitions are:
| Property value | Significance |
| 0 | Only the Microsoft Exchange Server directory service can modify the attribute. |
| 1 |
Users with at least the Modify Admin Attributes right can modify the attribute. |
| 2 | Users with at least the Modify User Attributes right can modify the attribute. |
| 3 |
Users with at least the Modify Permissions right can modify the attribute. |
For more information, see About Directory Security.