On the Start menu, point to
Programs, point to Administrative Tools, and then
click Active Directory Users and Computers.
In the console tree, expand the Windows 2000 domain.
Double-click Users, or double-click the node that contains
the recipient information you want to modify.
In the details pane, double-click the mailbox-enabled user you
are modifying.
On the Exchange General tab, click Delivery
Restrictions.
In the Delivery Restrictions dialog box, under
Message restrictions, select From everyone.