I contacted Twilio to set up my Filemaker database to text short messages to a group of clients. The attached image was their detailed response, but it specifies it is for FMP 13. I have FMP 11 on my host computer and about 8 older model iMacs & MBPs with FMP 10s & 11s on older version OS's. Not practical for me to upgrade all of these.
I asked Twilio if this would work on Models 10 & 11 & they said to find out if Filemakers versions 10 & 11 have support for HTTPS POST connections. If not, they said I might find a plugin that can act as a middle platform between filemaker & Twilio.