Messages to one or more domains accumulate in the delivery queue with a status indicating that the encryption is too weak.
Queue Status Message: 403 4.7.0 encryption too weak 0 less than 168
The destination mail server requires TLS encryption for the SMTP connection but Messaging Gateway is not configured to attempt TLS encryption for message delivery.
SMG should be configured to attempt TLS encryption for message delivery. To enable "opportunistic TLS":