You have an Exchange organization. All servers in the organization have Exchange Server
2010 Service Pack 1 (SP1) installed.
The organization contains five Hub Transport servers. All of the Hub Transport servers are
listed as source servers for a Send connector to the Internet.
You need to prevent a Hub Transport server named Hub1 from sending and receiving e-mail
messages from the Internet. The solution must meet the following requirements:
Ensure that Mailbox servers can deliver e-mail messages to Hub1.
Ensure that all other Hub Transport servers can deliver e-mail messages to the Internet.
What should you do on Hub1?

A.
Suspend all message queues.

B.
Stop the Microsoft Exchange Transport service.

C.
Disable all Receive connectors and Send connectors.

D.
Stop the Microsoft Exchange Mail Submission Service.

Explanation:
The first thing you do is suspend the queues on Hub1.
Then, you modify the Internet Send connector and remove Hub1 as a source server.
Finally, you modify the default receive connector for Hub1 to disable Anonymous
permissions.

http://technet.microsoft.com/en-us/library/bb124034.aspx
http://technet.microsoft.com/en-us/library/bb125022.aspx