Source note · Troubleshooting business SMS that is not delivered
After a user opts out, subsequent outgoing Twilio messages from the account to that user fail asynchronously with error 21610 rather than being rejected at API submission.
Checked 2026-10-02
any subsequent outgoing messages from your account to this user will fail with Error Code 21610 asynchronously
- Vendor
- Twilio
- Product
- Twilio Programmable Messaging
- Subsystem
- opt-out handling
- Deployment
- multi-tenant
- Region
- not restricted
- Release range
- current as of 2026-10-02
- Checked
- 2026-10-02
Sources
- Advanced Opt-Out for Messaging Services — Twilio · tier 2 current vendor documentation · opt-out behaviour section
Cite this note
APA
WarmTransfer. (2026, October 2). Troubleshooting business SMS that is not delivered: source note business-sms-delivery-troubleshooting-optout-21610-async. WarmTransfer. https://warmtransfer.net/knowledge/claims/business-sms-delivery-troubleshooting-optout-21610-async
BibTeX
@misc{warmtransfer-claim-business-sms-delivery-troubleshooting-optout-21610-async,
title = {Troubleshooting business SMS that is not delivered: source note business-sms-delivery-troubleshooting-optout-21610-async},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/business-sms-delivery-troubleshooting-optout-21610-async},
note = {Source note business-sms-delivery-troubleshooting-optout-21610-async, checked 2026-10-02}
}