Here is a summary of the provided text in one paragraph: Opt-in and opt-out text messages are crucial for businesses to engage customers without violating SMS regulations. Businesses must obtain explicit consent from customers before sending promotional messages, using a double opt-in method to confirm the recipient wants to receive such messages. Customers can opt-out by replying "STOP" or another designated keyword, and businesses must honor these requests promptly. Different governments and carriers have varying requirements for businesses sending promotional messages, with the US having regulations like the Telephone Consumer Protection Act (TCPA) that stipulate disclosure of terms and conditions, as well as adherence to specific best practices. To ensure compliance and manage subscriber lists effectively, businesses can use a messaging platform with native tools, such as Twilio MessagingX, which provides default opt-out keywords and resubscribe options.