Why do my SMS messages fail to send?

Question

Scenario A

I receive one of the error messages below when I send an outbound Text message:

We couldn't deliver this message

We couldn't send the message

Scenario B

When I review the message details in my Text history, the status of my message is either Undelivered or Failed:

Why are my SMS messages failing?

Answer

Multiple reasons exist for SMS message failure. Common reasons why SMS messages fail to send:

The destination handset is unreachable

The destination phone number doesn't support Text

The end user sent an opt-out code to one of my messages. For more information on opt-outs, see About opt-out keywords for Zendesk Text.

The destination phone number is located in a country where the Text number doesn't support SMS long code international messaging. For example, Zendesk US text numbers can't send SMS messages to UK numbers. For more information, see Twilio's SMS guidelines.

If SMS messages still fail to send or if I need my US/CA toll-free numbers verified, Contact Zendesk Customer Support for further help. with the ticket ID where the SMS message failed.