Having the word stop and out be the trigger for when someone wants to opt out of SMS text messaging is fine. But when people use those words in other contexts it should not block them in your system. For example just the other day someone texted me to say they would be out of town and couldn't make the scheduled time. And I was unable to respond to them because it blocked them thinking they wanted to opt out.

So the whole way that is approached needs to be improved because it's really problematic if a client contacts me to say hey I need help to stop smoking or a client telling me they're out of town, and I cannot even respond to them because all I have is a text message number and they've already opted out in their message because of the system is interpreting their use of the word stop or out.

Perhaps if it could be enforced that the word has to be on its own line in all capitals then it would not misinterpret something written as part of a sentence.