To correct this error, a new certificate that matches the FQDN of the Send connector or Receive connector that tried to validate this certificate must be created.
For more information, see Understanding TLS Certificates.
This status message indicates that the Microsoft Exchange Transport service was unable to validate the certificate chain, or that the public key that was used to validate the certificate signature is not the correct key.
This status message indicates that the revocation server for the certificate could not be reached.
In some cases, this is a temporary error because the revocation server is malfunctioning.
Check that you have a network connection and that your Team Foundation Server is available.
If the problem persists, contact your Team Foundation Server administrator.
This status message indicates that you must enable the certificate for use in the current application.
For example, if you're trying to use this certificate for Domain Security, the certificate must be enabled for SMTP.
By default, the certificate that installed with Exchange Server 2010 is self-signed.
It's generally a best practice to use certificates from trusted third-party certification authorities (CA).
Otherwise, make sure that this computer can access the revocation server.
If there is a firewall or proxy server in between this computer and the revocation server, make sure that your computer is configured to traverse the obstacle.
For more information about how to enable certificates, see Enable-Exchange Certificate.