Your network contains two Exchange Server 2010 Edge Transport server and five Exchange Server
2010 Hub Transport servers. All e-mail sent from your organization to the Internet is transferred by
the Edge Transport servers. You need to recommend a security solution for the organization to meet
the following requirements:
• Ensure that users can send encrypted messages to any other organization on the Internet
• Ensure that all Exchange related communication between Hub Transport servers and Edge
Transport servers is encrypted.
What should you recommend?

A.
Deploy IPsec.

B.
Deploy SMTP over SSL.

C.
Implement Domain Security.

D.
Implement Security/Multipurpose Internet Mail Extensions (S/MIME)

Explanation:
S/MIME provides a consistent way to send and receive secure MIME data. Digital signatures provide
authentication, message integrity, and non-repudiation with proof of origin. Encryption provides
data confidentiality. Compression can be used to reduce data size.
http://www.networksorcery.com/enp/data/smime.htm