Affects outbound directory exchange and allows only users in the specified GroupWise domains to appear in the Microsoft Exchange address book when directory synchronization and exchange are enabled. Users from all unlisted domains are blocked. See Section 8.1, Enabling Directory Synchronization and Exchange of Address Books
See also /blockdom.
IMPORTANT:Do not use the /allowdom and /blockdom switches together. If both are specified, only the /allowdom switch takes effect.