---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/80901#article
headline: "80901: Message Matched Stop Word"
url: https://www.twilio.com/docs/api/errors/80901
inLanguage: en
dateModified: 2026-06-08T12:04:59.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 80901: Message Matched Stop Word

Log Type: CARRIER

Log Level: WARNING

## Description

Proxy generated this warning because it did not forward an inbound SMS that matched a reserved opt-out keyword, or another opt-in or opt-out keyword that Proxy did not forward. By default, Proxy drops opt-out keywords instead of proxying them between participants. Dropped messages do not trigger callbacks.

### Possible causes

* A participant sent a single-word opt-out keyword such as `STOP`, `REVOKE`, `OPTOUT`, `UNSUBSCRIBE`, `END`, `CANCEL`, `QUIT`, or `STOPALL`.
* A participant sent one of the French opt-out keywords that Proxy blocks, such as `ARRETT`, `ARRET`, or `ARRETE`.
* A participant sent `UNSTOP`, which Proxy does not forward even though Proxy forwards other opt-in, help, and info keywords between participants.
* Your application expected Proxy to forward one of these reserved keywords, but Proxy handled it before the message could be proxied.

### Possible solutions

* Ask participants not to send reserved opt-out keywords as standalone messages if the message should be delivered through Proxy.
* If the sender previously opted out and needs to receive messages from the Twilio number again, have them send `START` to opt back in.
* Design your workflow so you do not depend on callbacks for blocked opt-out messages. Proxy does not trigger callbacks for messages it drops.
* If you need custom handling for opt-in or opt-out keywords, contact Support to enable the `ProxyRespectSmsStopFilterFlag` account flag and then use `InterceptCallbackUrl` on your Proxy Service to apply your logic.

#### Additional resources

* [Opt-out keywords](/docs/proxy/opt-out-keywords)
* [Webhooks](/docs/proxy/api/webhooks)
* [Twilio support for opt-out keywords (SMS STOP filtering)](https://help.twilio.com/hc/en-us/articles/223134027-Twilio-support-for-STOP-BLOCK-and-CANCEL-SMS-STOP-filtering-)