Following the update to Messaging Gateway (SMG) 10.7.3, attempting to connect to the Control Center web application fails with an SSL error immediately or fails after being prompted by the browser to select a certificate.
Messaging Gateway 10.7.3 now requests a client certificate as part of the TLS security negotiation. If any client certificate is presented before SMG is configured to trust it or the Certificate Authority that signed it, SMG will refuse the connection with an SSL error.