The Messaging Gateway (SMG) control center is unable to communicate with the SMG scanner resulting in a number of potential issues:
2018-01-09T21:41:13+05:30 (ERROR:2422.54671328):  Error creating new connection: Unknown error 336150661.
Jan 09 2018 21:41:13 [BrightmailScheduler_Worker-33] [ScriptHelper] ERROR - com.symantec.smg.controlcenter.BrightmailException: The Agent running on 127.0.0.1 is temporarily unreachable. Please check the specified host. ; nested exception is: java.net.SocketException: Connection reset
The workaround is to restart the agent service on each SMG scanner, one at a time. This should alleviate the issue temporarily.
On the command line run "service agent restart".
If the issue persists, open a case with Symantec Support.