Understanding SMS Error 21610: Recipient Unsubscribed (STOP)
Overview
When sending SMS or MMS messages through your CRM, you might receive an error indicating that a message could not be delivered because the recipient is unsubscribed. This error, often labeled with a code like 21610, is a compliance measure that respects the recipient's communication preferences and adheres to messaging regulations.
What Does This Error Mean?
This error means the person you are trying to contact has indicated they do not wish to receive messages. This can happen because they previously replied with a keyword like "STOP" to a message from your phone number, or because they have a "Do Not Disturb" (DND) status enabled on their contact profile within the CRM.
Why Does This Happen?
- The recipient sent a stop request, such as "STOP," "UNSUBSCRIBE," or a similar keyword.
- The contact's phone number may have been reassigned by their carrier to a new person who has not consented to receive your messages.
- The contact has a DND status activated for SMS, calls, or all communications in their profile.
- The CRM platform is preventing the message from being sent to maintain regulatory compliance.
How to Resolve the Issue
- Remove Unsubscribed Contacts: Clean your contact lists by removing numbers that have opted out.
- Request Re-subscription: The recipient must voluntarily re-subscribe by sending a keyword like "START" or "YES" to your number. You cannot manually override their opt-out status.
- Verify Consent: Always ensure you have explicit permission from contacts before adding them to your SMS lists.
Understanding Opt-Out Behavior
When you attempt to send a message to an unsubscribed number, the underlying messaging service will return an error, and the message will not be delivered. You will not be charged for this attempted send.
Common Opt-Out Keywords: Messages are blocked if a recipient has replied with STOP, STOPALL, UNSUBSCRIBE, CANCEL, END, or QUIT.
Common Opt-In Keywords: To resume receiving messages, a recipient must reply with START or YES.
Important Considerations
If a contact opts out of a specific messaging service number, that opt-out may apply to all numbers associated with that service. The most important rule is to always obtain proper consent and honor unsubscribe requests immediately.
Frequently Asked Questions
Am I charged for a message that is blocked due to an opt-out?
No. The message is not sent, so you are not charged for the attempt.
Can I manually re-add a contact who opted out?
No. The contact must initiate the re-subscription themselves by texting an opt-in keyword to your number.
If someone opts out of one number, are they blocked from all my numbers?
It depends on the configuration. An opt-out from a single phone number typically only blocks that number. However, an opt-out from a messaging service can block all numbers linked to that service.
What is the difference between an opt-out and a DND status?
An opt-out is triggered when a recipient replies with a keyword like STOP. A DND status is a setting managed directly on the contact's profile that blocks communications, independent of any keyword reply.
Why would a number that never opted out be blocked?
The phone number may have been reassigned to a new user who did not consent, or the contact may have a DND status enabled in their profile.
How can I prevent these errors?
Only message contacts who have explicitly opted in, regularly maintain your contact lists by removing unsubscribed numbers, and promptly honor all stop requests.