Messages not arriving to users

I am having the same problem as in this thread: https://www.symantec.com/connect/forums/messages-not-arriving-users 

There are no instructions in that thread on what to do if the problem occurs, except send some sample to a random email address that isn't even part of symantec (brightmail??) ... I am not understanding how you don't have a proper process for resolution of email problems? Especially when you do not give clients any indication that messages are failing to be delivered.

Please advise.