You are evaluating the implementation of Exchange Server 2010 SP1 Edge Transport servers and Hub Transport servers in adatum.com. You need to recommend a solution to ensure that the Exchange Server 2010 SP1 servers can queue email messages for humongousinsurance.com.

What should you include in the recommendation?

A.
a remote domain

B.
a retention policy

C.
an authoritative domain

D.
an external relay domain