SMG spam definitions stop updating but virus definitions update normally.
In the conduit_log you see the error:
"Error from web server 471 - License Invalid : unable to GET: https://aztec.brightmail.com/rules..."
License for Brightmail Antispam is not correct, is expired or has a start date in the future.
Open the file in a text editor and verify the start date and end date. The fields look like:
If the <end_date> field is dated in the past, you will need to install a currently valid license.
If the <start_date> field is dated in the future, wait until the day after the start date and then follow these steps:
If the issue persists, please contact Symantec Technical Support.