In the graphical user interface (GUI) of the Control Center, underStatus->System->Dashboard, under the System Status section, it is showing that the AntiVirus definitions, called "Virusdefinitions" on that screen get updated within the last day but the AntiSpam definitions, called "Spam definitions" on that screen are 2 days or older on a Symantec Messaging Gateway appliance.
In the Status -> System -> Logs, with the Filter settings of Host: All Hosts and Component: Scanner, there are various errors of the type "Conduit", for example: "Network error occurred, Connect failed....."
The AntiSpam definitions are downloaded from a different location than the AntiVirus definitions and the relevant port has not been opened in the firewall.
AntiVirus definitions are updated through port 80 using the LiveUpdate technology from the liveupdate.symantec.com servers. AntiSpam definitions are updated through port 443 using the Conduit technology from the aztec.brightmail.com servers. In order to register the license, download software updates and download AntiSpam definitions, port 443 needs to be opened in the firewall for the relevant hosts.
More information about which ports and hosts which needs to be opened can be found in the Installation Guide and here:
 Network error occurred, Connect failed; operation now in progress (7), check your network connection settings, check your proxy settings (if applicable), and check to ensure that port 443 (HTTPS) is open through any relevant firewalls.