Summary

Internet communications security can take a number of forms, from using exotic physical security devices like pressurized fiber- optic cables to simpler, more affordable solutions like IPSec. You can add protection to your Exchange servers by deploying IPSec (both for server-to-server and client/server communications), using SSL to protect SMTP traffic as it flows between servers, and using ISA to allow RPC traffic from external Outlook users to safely reach your Exchange mailbox servers. RPC over HTTPS allows an extra degree of flexibility, particularly if you front it with ISA Server.