Learn more about assigning a certificate to Exchange services
You need to assign a certificate to one or more Exchange services before the Exchange server is able to use the certificate for encryption. Once you assign a certificate to a service, you can't remove the assignment.
You don’t need to replace the Microsoft Exchange self-signed certificate to encrypt SMTP traffic between Exchange servers and services in your organization. You need additional certificates to encrypt SMTP connections between Exchange servers and external messaging servers.
For more information, see the following topics:.