mobile not receiving text messages from my computer

I have a custom program to send messages to club members from my computer through an smtp server.  This had been working for quite a while but recently the messages are not getting through.

the message is sent like this  [email address removed per the Verizon Terms of Service] 

i believe they are being filtered out(spam detection?) by verizon.

What are the requirements to get the messages delivered and how can tell why they are not being delivered?