Error 21614 occurs when you attempt to send an SMS to a destination number that is not recognized as a valid mobile number. In many cases, the number is a landline, is formatted incorrectly, or uses an unsupported non-standard number format.

TABLE OF CONTENTS

What Is Error 21614?

Error 21614 means the destination number cannot be validated as a mobile number that can receive SMS.

This can happen when:

  • The number is a landline.

  • The number is invalid or incomplete.

  • The number is formatted incorrectly.

  • The destination uses a non-standard IoT or machine-to-machine number format.


Key Benefits of Validating Mobile Numbers

Checking destination numbers before sending helps reduce failed messages and improve contact data quality.

  • Fewer Messaging Failures: Avoid sending SMS to numbers that cannot receive them.

  • Cleaner Contact Records: Identify invalid or incorrectly formatted phone numbers earlier.

  • Improved Deliverability: Focus messaging on valid mobile destinations.

  • Better Automation Reliability: Reduce workflow failures caused by unsupported numbers.


Common Causes of Error 21614

Error 21614 commonly appears when the destination number is not eligible for SMS delivery.

Common causes include:

  • The phone number belongs to a landline.

  • The phone number is missing digits.

  • The number uses the wrong country code.

  • The number is not in E.164 format.

  • The number contains an incorrect local prefix.

  • The number belongs to an IoT or M2M service that uses a non-standard numbering format.

  • Imported or manually entered contact data is incorrect.


How to Fix Error 21614

Start by checking whether the destination number is a valid mobile number.

  1. Open the affected contact or destination number.

  2. Confirm the number belongs to a mobile device.

  3. Verify the country code.

  4. Format the number using E.164 format.

  5. Remove unnecessary spaces, punctuation, or local dialing prefixes.

  6. Save the corrected number.

  7. Retry the message.

If the number is confirmed to be a landline, SMS cannot be delivered to it through a standard mobile messaging route.


Use E.164 Phone Number Format

Use E.164 formatting whenever possible.

The expected structure is:

+[country code][subscriber number]

For example:

+14155552671

Using a complete international format helps the system identify the number correctly.


Check Whether the Number Is Mobile or Landline

A phone number may look valid but still be unable to receive SMS.

If you are unsure whether the destination is mobile:

  • Confirm the number type with the recipient.

  • Use an available number lookup or validation tool.

  • Check whether the number has recently been ported or reassigned.

If the number is a landline, use another supported communication method instead of SMS.


IoT and Machine-to-Machine Numbers

Some IoT and machine-to-machine numbers use numbering formats that differ from standard mobile numbers.

These numbers may:

  • Contain additional digits.

  • Use unusual prefixes.

  • Follow country-specific formats.

  • Fail standard mobile-number validation even when they are active.

If you believe the number is a valid IoT or M2M destination but it continues to fail validation, contact support for assistance.


Check Automated Workflows and Imported Contacts

If Error 21614 appears during an automated send, the problem may be stored in the contact record or data source.

Review:

  • Imported phone numbers

  • Form submissions

  • Contact phone fields

  • Workflow destination fields

  • Custom phone fields

  • Numbers copied from spreadsheets or external systems

Correcting the source data can prevent the same error from affecting future messages.


Frequently Asked Questions

Q: What does Error 21614 mean?
It means the destination number is not recognized as a valid mobile number for SMS.

Q: Can I send SMS to a landline?
Not through a standard mobile SMS route. Use another supported communication method if the number cannot receive text messages.

Q: Can incorrect formatting cause Error 21614?
Yes. Missing country codes, incomplete numbers, or invalid prefixes can trigger the error.

Q: What format should I use for the destination number?
Use E.164 format with a plus sign, country code, and complete subscriber number.

Q: Can IoT or M2M numbers trigger this error?
Yes. Some non-standard IoT or M2M numbering formats may fail normal mobile-number validation.

Q: Can imported contacts cause this error?
Yes. Incorrect or incomplete numbers imported from another system can generate Error 21614 during messaging.


Need Help?

If Error 21614 continues after reviewing the destination number, first confirm that the number is a valid mobile number and is formatted correctly.

Verify that:

  • The destination is a mobile number capable of receiving SMS.

  • The number is not a landline.

  • The correct country code is included.

  • The number is formatted in E.164 format.

  • The number contains all required digits.

  • There are no typos, extra characters, or invalid prefixes.

  • Imported or form-submitted contact data was saved correctly.

  • The workflow or campaign is using the correct phone field.

  • The destination is not using an unusual IoT or M2M numbering format that may fail standard validation.

If the number is confirmed as a valid IoT or M2M destination but still fails, contact support for additional review.

If the issue continues, collect the sender number, destination number, recipient country, number type if known, message type, workflow or campaign name if applicable, and a screenshot of Error 21614 before contacting support.