Veriizon Wireless failed to deliver multiple messages today 4/26/15, between 0500 and 0540 hrs during a callout (SoCal). I contacted VZW customer service and reached 2nd level support and they said the trouble "had" to be at the sending end (which we know isn't likely). I have a contact number at VZW for 2nd level support and they are open to having a conference call with a Mission Manager technical rep. Please contact me to set up a call.
I have also looked into a VZW service called Enterprise Messaging which appears to be a "pre-screened" service for organizational messaging. There seems to be a charge (unknown amount), a pilot number, static IP requirement for message origin, and the use of a different message delivery domain (@vzemag.biz). The service may be restricted to large corp. or government accounts, not certain.