30630: Attempt to send to unsubscribed recipient

This error occurs when you try to send a message to a recipient who has opted out of messages from your Twilio phone number, Channels sender, or Messaging Service. Twilio blocks the send until that recipient opts back in. For long code and toll-free messaging, Twilio handles standard opt-out keywords automatically. If you use Advanced Opt-Out with a Messaging Service, Twilio can also enforce the custom opt-out keywords you configure.

• The recipient previously replied with a standard opt-out keyword such as STOP, UNSUBSCRIBE, END, QUIT, STOPALL, CANCEL, REVOKE, or OPTOUT to the sender you are using. (help.twilio.com)
• The recipient matched a custom opt-out keyword configured through Advanced Opt-Out on your Messaging Service.
• Your application is still sending from the same Twilio phone number, Channels sender, or Messaging Service after the recipient opted out and before they opted back in.

• Stop sending to this recipient from the affected sender or Messaging Service. Remove the recipient from your campaign or store the opt-out in your own suppression list so you do not retry the send. If you use more than one sender, maintain your own block list across those senders as well.
• Ask the recipient to opt back in with a supported opt-in keyword. Twilio supports START, YES, and UNSTOP for long code opt-ins. For toll-free re-subscribe flows, use START or UNSTOP. (help.twilio.com)
• If you send through a Messaging Service, enable and configure Advanced Opt-Out so you can manage opt-in, opt-out, and help keywords consistently and track these events with the OptOutType webhook parameter.
• Review your consent flow before sending more messages. Send messages only to recipients who have expressly opted in, and include clear opt-out instructions in your messaging program.

• Customize users' opt-in and opt-out experience with Advanced Opt-Out
• Messaging Services
• Twilio support for opt-out keywords (SMS STOP filtering)