Example of alert/notification being generated:
"Symantec Messaging Gateway Alert Notification for [email protected]
Spam quarantine exceeds maximum size threshold (10,737,418,240 bytes). Current disk space utilization is 204% (21,935,362,048 bytes) of the configured maximum size."
Quarantine limits under Spam->Quarantine Settings are not set and configured with default settings.
Alerts settings under Administration->Settings->Alerts->Disk Space are enabled by default for the setting "Usage of the maximum configured disk space for Spam Quarantine exceeds" and set to 120%
This has been confirmed as "working as designed" situation by Symantec engineering team. SMG official documentation will be updated to also reflect this state.