You have an Exchange organization. All servers in the organization have Exchange Server
2010 Service Pack 1 (SP1) installed.
The network contains internal DNS servers.
You need to ensure that the Hub Transport servers use external DNS servers when they
resolve Internet names.
What should you modify?

A.
the message delivery properties of the Hub Transport global settings

B.
the properties of the default remote domain

C.
the properties of the Hub Transport server object

D.
the properties of a Send connector

Explanation:
Configured on the Hub Transport server properties window, External DNS lookups tab.

http://technet.microsoft.com/en-us/library/bb123514.aspx