Submissions can be restricted to a limited number of security principles though the standard Windows Discretionary Access Control List (DACL). This feature prevents non-trusted senders, such as unauthorized Internet users, from sending mail to an internal only distribution list. An example of this would be an “All Employees” distribution list which should not be available to anyone outside the company (by spoofing or otherwise). Note Restricted distribution lists will only work on the bridgehead servers or SMTP gateway servers running Exchange 2003.