After an SSL certificate has been installed on an Exchange Server 2010 server you can assign different Exchange services to use that certificate.
To assign a service to a certificate launch the Exchange Management Console. Navigate to Server Management, and select the server that has the certificate installed.
If you encounter an error message of “The certificate is invalid for exchange server usage” see this article for the solution.
Right-click the certificate you wish to assign and choose Assign Services to Certificate.
Click Next to continue the wizard.
Choose the services you wish to assign to the certificate. In this example I am choosing IIS so that the certificate can be used for OWA, ActiveSync, etc.
Click Assign to execute the change.
When the task has completed successfully click Finish to close the wizard.
The certificate will now appear with the chosen services assigned to it.