Handling High Volume SMS Errors

High Volume SMS provides detailed error codes for reasons why a SMS may have failed sending or delivery which can be used to determine how to adjust your campaigns.

Error Code Structure

Error codes are composed of a prefix and a number. The prefix identifies the error reporting party and the numeric code is aligned with HTTP response status codes. In the following error code, SMS-CAR-411, SMS-CAR- is the prefix and 411 is the numeric code.

Error Reporting Party Prefix

For SMS, there are 3 parties that can return an error:

Error / Status Numbers

The numerical portion of the error follows a subset of HTTP status conventions:

1. Informational responses (100–199)
2. Client errors (400–499)
3. Server errors (500–599)

Common Errors

Commonly encountered errors fall into categories:

1. Sending to invalid numbers such as landline numbers or other numbers that cannot support texting.
2. Being rejected as spam.

Invalid Number

When you receive an error that indicates a number is invalid or unavailable (e.g. SMS-UP-410, SMS-UP-411, SMS-UP-412, SMS-UP-413), you should make a note of it and consider stopping messages to that number. You can also ask your user to confirm the validity of their number (via SMS) before resuming messages.

A common reason for this is texting to landline numbers that do not have texting capability. An API service like NumVerify can be used to check whether a number is a landline number (without texting capability) or a mobile number (likely with texting capability).

Spam

If are receiving a lot of spam rejections, your users may be indicating this is spam or the carrier may be using spam detection algorithms. In this case, you should consider changing your message so it is not recognized as spam. After you change your message, you may want to consider provisioning a new phone number with the updated messages as your existing number may be blacklisted.

Different recipient wireless carriers will have different spam policies so it may be worthwhile to check errors against recipient carrier. An API service like NumVerify can also be used to identify the recipient's wireless carrier.

Expected Errors

Some information is provided for informational purposes and while it may be classified as an error, may be expected from carriers. For example, it may not possible to get delivery status from carriers as reported by SMS-CAR-104 and SMS-CAR-199. When checking for delivery success and failure, you may want to verify receipt of the SMS message before classifying these as non-delivered.s

Error Code List