Hello @MichaelAndConnie ,
You can technically send as many SMS messages as you want, jut bear in mind what tier of SMS messaging you're signing up for. If you're sending daily texts to hundreds, or even thousands of contacts, it can add up very quickly. If you end up going over the tier you initially paid for, you'd be charged at the higher tier for the following month.
For more info on SMS functionality, I'd recommend taking a look at these articles:
SMS Overview
SMS Guidelines
SMS Best Practices
... View more
