Opt-out language must be included in automated texts in order to comply to the industry's guidelines and standards. Phone carriers are beginning to enforce this rule and offending numbers are starting to find a lot of their texts being blocked and marked as a carrier violation. If you want to improve your deliverability, or to avoid any possible shutdowns to your sms outbound capabilities, consider including this to your automated texts so that the recipient is aware of the option they have to stop receiving future messages.
What is opt-out language?
You've most likely seen opt-out language like Reply STOP to unsubscribe at the end of an automated text before. It's an addition to let the end client know that they have the option to stop receiving messages. Typically it's added to the end of the message.
The initial message to a contact as well as any following message after a short break in time must include Reply UNSUB to unsubscribe or similar using the one of the following opt-out keywords: UNSUB, OPTOUT, STOP, STOPALL, UNSUBSCRIBE, CANCEL, END, or QUIT.
When setting up your campaigns, there is an option to include the opt-out verbiage automatically. This option is available when selecting the Send Sms option.