As part of the DigiCert acquisition of Symantec’s Website Security and related PKI solutions, our digital certificates will now be issued from the DigiCert public certificate authority. We expect to issue all new public TLS certificates from this hierarchy starting from November 28, 2017.
Any certificates issued/renewed across the Email Security.cloud infrastructure from this date forward will use the DigiCert public roots. In most cases, this change will not cause an issue, however some customers may have configured their MTAs to trust only specific root certificate authorities; these customer’s MTAs would fail to connect to Symantec’s Email Security.cloud if their servers don’t trust the DigiCert public root certificate.
Review the following KB articles:
to learn more about the Web PKI Hierarchy change
to learn more about how this change affects the Email Security.cloud service