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":

1. Log into the Control Center as an adminstrator
2. Go to Administration > Host configuration > host > SMTP > Advanced settings > Delivery
3. Check " Attempt TLS encryption for delivery of all messages "
4. Click Continue
5. Check "Apply above settings to all scanner"
6. Click Save