Office Communications Server requires certificates on each Standard Edition server or Enterprise Edition server in order to use mutual TLS (MTLS), which is TLS with mutual authentication. All Office Communications Servers use MTLS to communicate with one another. If you do not configure MTLS on each server, presence and instant messaging (IM) communication may not work properly.

Each client also needs to trust the certificate that the server is using in order to connect to the server by using TLS. You can use the Certificates Wizard on a Standard Edition server or Enterprise Edition server to:

You cannot use the Certificates Wizard to request or assign the certificate to the Web Components Server. Instead, the certificate must be requested, or requested and assigned, by using the Internet Information Services (IIS) certificate wizard as explained in Configure the Web Components Server IIS Certificate.

Use the certificate assignment procedures that are appropriate for your deployment scenario.

For details about submitting a request to a public certification authority (CA), see Generating an Offline Request for a Public Certification Authority.