Hello,
What version of SEP are you running?
In case, of SEP 11.x, please check out the below link:
How to configure mobile computers to automatically download virus definitions when disconnected from the Symantec Endpoint Protection Management console
http://www.symantec.com/docs/TECH104571
In case, of SEP 12.1, please check out the below link:
Configuring mobile computers to automatically download definitions when disconnected from the Symantec Endpoint Protection 12.1 Management console
http://www.symantec.com/docs/TECH177361
Hope that helps!!