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Twilio is a cloud communications platform that enables developers to programmatically send and receive SMS messages, make and receive phone calls, and perform other communication functions using its web service APIs. It is widely used in applications for customer engagement, notifications, and two-factor authentication.
When using Twilio's SMS API, you might encounter the error code 21421. This error indicates that the 'To' phone number is not currently reachable via SMS. This can be a common issue when sending messages to recipients who may have network issues or incorrect phone numbers.
Error 21421 is a specific error code returned by Twilio when an SMS message cannot be delivered to the intended recipient. This typically occurs when the recipient's phone number is either incorrect, inactive, or not capable of receiving SMS messages at the time of sending.
To resolve this issue, follow these actionable steps:
Ensure that the phone number is correct and formatted according to the E.164 standard. This format includes the country code, area code, and the local number.
Contact the recipient to confirm that their phone is turned on and within network coverage. You can also use Twilio's Lookup API to check the phone number's status.
Verify that the recipient's phone number is capable of receiving SMS messages. Some numbers, such as landlines, may not be SMS-enabled.
For more information on handling Twilio errors, visit the Twilio Error Code Documentation. You can also explore the Twilio SMS API Documentation for further guidance on sending messages.
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