Messaging Server offers the following sets of security features:
Protecting Messaging Components in Your Deployment
Planning User Authentication
These options enable you to determine how your users will authenticate to your mail servers, preventing unauthorized users from gaining access to your system.
Understanding Security Misconceptions
Using this set of options, you can perform user authentication and protect the message itself by using authenticated SMTP and certificates for digital signatures, encryption, and Secure Sockets Layer (SSL).
See Chapter 13, Planning Messaging Server Security for more information.