cmdlet so as to create a new internal transport certificate (it is also referred as direct trust certificate) on the same computer that returned this Warning event. It actually creates a Simple Mail Transfer Protocol (SMTP)-enabled certificate for direct trust.
If this warning was occurred on a "Hub Transport server", you have to create the internal transport certificate on the Hub Transport server where the warning occurred initially. After you create the certificate, restart the Microsoft Exchange EdgeSync service to update the certificate information on the Edge Transport servers that are subscribed to the organization.
If this warning was occurred on an Edge Transport server, you have to create the internal transport certificate on the Edge Transport server where the warning occurred. After you have created the certificate, resubscribe the Edge Transport server to the Exchange organization to update the certificate information in Active Directory.
In case you are not running the Microsoft Exchange EdgeSync service, you must manually update the certificate. For more information, see http://go.microsoft.com/fwlink/?LinkID=30939&l=en&id=6bb98d10-6f12-4b08-a58e-36375f605d65.
Hope it helps.
Thanks and Regards