When Messaging Gateway (SMG) is configured to deliver filtered messages to the Spam Quarantine but an LDAP source configured in Directory Integration is offline or inaccessible, messages destined for the Spam Quarantine are rejected by the quarantine and accumulate in the delivery queue. Viewing the delivery queue on any scanner host via the Control Center Status > Message Queues page shows messages for the Control Center route delayed with a "421.x.x connection closed by Controlcenter" message.
421.x.x connection closed by Controlcenter
This occurs when the Control Center web application fails to connect to a configured Directory Data Source. The connection or authentication error causes the message to be deferred by the web application SMTP interface.
Note that the Spam Quarantine does not need to be enabled for end users or configured to validate recipient addresses for this to occur. The Control Center attempts to connect to the data source regardless of the quarantine configuration and a failure to do so results in message delivery to the quaranting being deferred.
This is a known issue and will be addressed in a future release of the product. Please subscribe to this article to be automatically notified of updates.