You have an Exchange Server 2013 organization named contoso.com that contains 10 servers.
Your company purchases a company named Fabrikam, Inc. Fabrikam has an Exchange Server
organization named fabrikam.com. All of the email messages sent between the organizations is
routed over the Internet.
You need to ensure that the email messages sent from contoso.com to fabrikam.com are encrypted.
What is best way to achieve the goal? More than one answer choice may achieve the goal. Select the
BEST answer.
A.
Create a Send connector of type Partner.
B.
Instruct all of the users in contoso.com to use SMIME.
C.
Modify the Authentication settings for the Send connectors in contoso.com.
D.
Create a federation trust between the organizations.
If you want to ensure secure, encrypted communication with a partner, you can create a Send connector that is configured to enforce Transport Layer Security (TLS) for messages sent to a partner domain. TLS provides secure communication over the Internet.
https://technet.microsoft.com/en-us/library/jj657514(v=exchg.150).aspx