Twilio strives to provide the most reliable delivery statuses possible for all messaging worldwide. However, there are cases when users may see a message status of
Delivered, even when the message did not successfully reach the destination mobile device. This guide explains some of the possible causes of these false positive statuses, and how to troubleshoot them.
When Twilio sends a message, we update the message status to show
Sent. When we receive a notification from the carrier that the message has been sent to the destination, we change the status to
Delivered. This transition is explained in What are the Possible SMS and MMS Message Statuses, and What do They Mean.
The false positive delivery status may occasionally occur at this point due to the following issues:
- False positives to a single mobile device are likely caused by a device-specific issue.
- False positives to multiple users, can be caused by carrier filtering, issues with local telecom infrastructure, or technical limitations.
Please continue reading for more information and troubleshooting steps.
Messages sent using 10-digit local long code phone numbers to the United States and Canada
If your messages are application-to-person (A2P) traffic, and are being sent using standard 10-digit long code phone numbers to users in the US or Canada, these messages may be blocked by carriers to enforce rules and regulations. This is commonly referred to as carrier filtering.
In most cases, Twilio will receive an error back from the carrier when a message is filtered. We flag these responses with Error 30007.
Notice: In November 2019, Twilio observed an increase in false positive delivery statuses for messages sent to wireless phone numbers in the U.S. In these cases, the carrier was unable to return an error to Twilio advising the message was blocked. This caused some A2P long code messages to show a
Delivered status, despite being undelivered. As of December 17, 2019, Twilio has implemented a fix with our carrier partners to help ensure that these messages receive the correct
Undelivered status with Error 30007.
What should I do if I suspect my messages are being filtered?
For A2P messaging in the U.S. and Canada, using a short code number allows you to get your messaging use case approved in advance, and avoid carrier filtering. For more information, see What is a Messaging Short Code.
For A2P messaging to destinations in the U.S., toll-free phone numbers are designated for business messaging. While toll-free numbers specifically don't allow marketing or promotional messaging, they can offer reduced filtering on many kinds of transactional A2P messaging use cases. For more information, see Information and best practices for using Toll-Free SMS in the US and Canada.
Notice: Canadian carriers don't differentiate SMS coming from toll-free phone numbers. These messages will be filtered according to the same rules as standard long code traffic. For ensuring high deliverability on A2P messaging to Canada, a Canadian short code number is the best option.
For more information about phone number type messaging differences, see Comparison of SMS messaging in the US and Canada for long codes, short codes, and toll-free phone numbers.
I don’t think my messages are being filtered. What should I do?
If you are not sending A2P traffic via local long code numbers in the U.S. or Canada, or you have eliminated the other possibilities listed above, see the Messages Marked ‘Sent’ or ‘Delivered’ section of Troubleshooting Undelivered Twilio SMS Messages.
Messages sent to a country other than the U.S. or Canada
Twilio is continuing to work on increasing our reach and identifying the best possible carrier connections available worldwide. However, in some countries, local infrastructure or technical limitations of carriers may result in inaccurate delivery statuses.
To troubleshoot these issues, please use the below checklist:
- Is this issue affecting more than one user? False positive delivery statuses can be caused by issues specific to a mobile device, including poor cellular reception, or a device malfunction.
- Does the destination country require Alphanumeric Sender ID pre-registration? These countries tend to have strict rules about what types of messages can be delivered, and are likely to result in low delivery quality due to heavy carrier filtering without registering.
- Does your message align with Twilio's SMS Guidelines for the destination country?
For additional troubleshooting steps, see the Messages Marked ‘Sent’ or ‘Delivered’ section of Troubleshooting Undelivered Twilio SMS Messages.