Missing SMG host in Received: header

I noticed that our Symantec Messaging Gateway (10.6.1-4) servers are inserting improperly formatted Received lines with the host name is missing:

Received: from XXX.Example.com (XXX.Example.com [10.18.61.81])
    by  (Symantec Mail Security) with SMTP id 11.1A.12345.1A2B3C4D; Fri, 26 Aug 2016 13:12:34 -0700 (PDT)

The host name is required after the "by" and before the parenthesized comment.  I expect this is due to some mis-configuration on our part.   I noticed that the configured host name on "Edit Host Configuration" was not a FQDN.  I changed it to a FQDN, but the Received lines were still missing the host name.

Is anyone familiar with why this is happening, and what should be done to fix it?

Thanks....