This article provides a comprehensive guide to understanding and resolving common SMS delivery errors in the platform. By identifying typical failure points and offering practical solutions, you can enhance your messaging success rate and ensure effective communication with your contacts.
What Are Common Unsuccessful SMS Errors?
SMS delivery errors occur when a message cannot be delivered to the intended recipient due to issues like invalid numbers, carrier filtering, user opt-outs, or technical restrictions. Understanding these errors helps businesses maintain high message deliverability and comply with industry regulations.
Most of these errors originate from carriers, Twilio, or LC Messaging, and are represented by specific error codes. Identifying and interpreting these codes enables users to take corrective action quickly and confidently.
Key Benefits of Understanding SMS Errors
Recognizing and addressing SMS errors promptly can significantly improve your communication strategy.
- Enhanced Deliverability: By identifying common errors, you can take proactive steps to prevent message failures.
- Efficient Troubleshooting: Understanding error codes allows for quicker resolution of issues.
- Improved Compliance: Awareness of carrier and platform restrictions helps maintain compliance and avoid penalties.
- Optimized Messaging Strategies: Insights into errors can inform better messaging practices and content.
How to Identify and Interpret Common SMS Errors
Accurate diagnosis of SMS errors requires checking delivery logs, identifying the error code, and using the information to adjust your messaging or recipient data.
- Click on the Conversations tab from your account.
- Search for the SMS log that was unsuccessful.
- Click on the unsuccessful Conversation.
- Hover over the Red Triangle Error Box.
The dialogue box will display the numerical error code and a short description of the error for that conversation (e.g., Error 30034, Error 21610).
Common Error Codes and What They Mean
The following are the most frequently encountered SMS errors within the platform:
Description: The total size of the media message exceeds the maximum limit allowed by the messaging provider.
Resolution:
- Compress or resize the media file.
- Ensure the file stays within Twilio's supported MMS size limits.
- MMS (US/Canada): Maximum size is 5MB per message.
Description: The recipient has opted out of receiving messages by replying with STOP.
Resolution:
- Do not message this number again unless the user sends START to opt back in.
- Ensure proper opt-in mechanisms are in place.
Description: The recipient number can't be reached using the current 'From' number (e.g., due to carrier restrictions or unsupported international routes).
Resolution:
- Use a local or internationally enabled number.
- Confirm routing compatibility between 'To' and 'From' numbers.
Description: Your Twilio account was suspended between the time of message send and delivery.
Resolution:
- Contact Twilio Support to resolve account status.
- Ensure your account remains active for message queues.
Description: The recipient's phone is turned off, out of range, or temporarily unavailable.
Resolution:
- Retry the message later.
- Verify the number is active.
Description: The destination number is blocked from receiving this message.
Resolution:
- Confirm the number is valid and not carrier-blocked.
- Avoid messaging numbers with prior failed delivery history.
Description: The destination device is unreachable (e.g., turned off or out of range for an extended period).
Resolution:
- Retry after some time.
- Clean your list to remove unreachable or inactive numbers.
Description: The number cannot receive SMS — usually because it's a landline or incompatible with SMS.
Resolution:
- Remove landlines from your list using number validation tools.
- Confirm numbers support SMS before messaging.
Description: The message was blocked by the carrier for violating content policies or appearing as spam.
Resolution:
- Avoid spam-like content and shortened URLs.
- Use personalized, compliant messaging.
- Register your number with A2P 10DLC or Toll-Free verification.
Refer to for more context: How to Prevent SMS Filtering by Carriers: Error 30007
Description: You attempted to send a message to a U.S. number from a 10DLC number that is not associated with a registered A2P campaign.
Resolution:
- Register your number through Twilio's Trust Hub.
- Link the number to an approved Messaging Service.
- Confirm proper campaign association.
Description: An unspecified error occurred during message delivery.
Resolution:
- Check the message body for formatting or content issues.
- Test with a different number or content structure.
Description: This error often occurs when images fail to load or send in conversations.
Resolution:
- Check the domain's DNS configuration using MXToolbox. If the DNS records aren't found or not pointing to
brand.ludicrous.cloud, this can cause the image retrieval to fail. - Ensure a CNAME record is set up correctly, pointing your branded domain to
brand.ludicrous.cloud. - If this is missing or misconfigured, images will appear broken in conversations. Check out Branding System-Generated Links (API Domain).
Description: You attempted to send a message to a mobile number in a country that requires pre-registration and provisioning of a Numeric Sender ID. However, the Numeric Sender ID has not yet been provisioned with the carrier.
Resolution: If you believe your Numeric Sender ID is already registered, please gather at least three Message IDs that show an "undelivered" status with error code 30024. Once you have these, contact our Support team, and we'll review the registration status to help resolve the issue.
To explore additional error codes beyond those most commonly encountered in the platform, view the Full Catalog of Error Codes.
Additional Troubleshooting Tips
Understanding the technical side is helpful, but these best practices can proactively reduce errors:
A2P 10DLC and Toll-Free numbers go through a vetting process that improves delivery rates and reduces filtering.
Avoid all caps, spammy phrases, or including long URLs without a proper link shortener.
Use a conversational tone to avoid content blocks.
Ensure numbers are valid, formatted correctly, and that users have opted in.
Use the platform's reporting tools to spot patterns in delivery issues and make proactive adjustments.
Frequently Asked Questions
Was this article helpful?
That’s Great!
Thank you for your feedback
Sorry! We couldn't be helpful
Thank you for your feedback
Feedback sent
We appreciate your effort and will try to fix the article