Hello,
Check this Article:
Required exclusions for proxy servers to allow Symantec Endpoint Protection to connect to Symantec reputation and licensing servers
LiveUpdate connects via HTTP to the domains symantec.com, liveupdate.symantecliveupdate.com, and akamai.net.
If a connection fails, LiveUpdate tries to connect to one of the other listed domains. The listed domains may change because of server maintenance.
If LiveUpdate cannot make an HTTP connection, LiveUpdate connects via FTP to update.symantec.com/opt/content/onramp.
Hope this helps!!