Well I’ve done some experimenting and I’ve written a test bed that sends a text message through the Mail app just fine althigh it does require knowing the recipient’s service. I guess I’ll have to live with it if a free service doesn’t come along. RainedOut was free with ads but now they are “upgrading” to charging recipients which is not acceptable.
It’s not the ideal way I want to send text messages but it does work for sending to 100+ recipients.