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Understanding Common SMS Delivery Errors

Overview

Last updated: May 26, 2026

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On this page

  • What Are Common Unsuccessful SMS Errors?
  • Key Benefits of Understanding SMS Errors
  • How To Identify and Interpret Common SMS Errors
  • Step 1: Go to the Conversation Logs
  • Step 2: Locate and Identify the SMS Error Code
  • Common Error Codes and What They Mean
  • 1. Error 11751 – Media Message Size Limit Exceeded
  • 2. Error 21610 – User Opted Out
  • 3. Error 21612 – Unreachable 'To' Number from Current Sender
  • 4. Error 30002 – Account Suspended Before Delivery
  • 5. Error 30003 – Unavailable or Inactive Number/Unreachable destination handset
  • 6. Error 30004 – Message Blocked by Carrier
  • 7. Error 30005 – Unknown Destination Handset
  • 8. Error 30006 – Landline or Unsupported Number
  • 9. Error 30007 – Carrier Filtering (Spam or Policy Violation)
  • 10. Error 30034 – US A2P 10DLC: Message from an Unregistered Number
  • 11. Error 30008 – Unknown Error
  • 12. Error 11200 – HTTP retrieval failure
  • Additional Troubleshooting Tips
  • Frequently Asked Questions
  • Related Articles

In this folder

  • Phone System Pricing & Billing Guide
  • What is LC (Lead Connector) Phone System?
  • Number Intelligence - Spam Detection, Caller ID & SMS Validation
  • Voicemail For Company And For Users
  • Getting Started with A2P 10DLC
  • Call Forwarding to Your Bizura Phone Number
  • How do I migrate my agency and sub-account over to LC Phone?
  • Why is your account suspended
  • Regulatory Bundle and Address Creation for Sub-Accounts
  • How to Disable LC Phone System for Subaccount/Location (LC to Twilio)
  • Phone System Messaging Analytics Overview
  • Know Your Customer (KYC) in the United Kingdom
  • How to Enable Call Transcriptions for Recorded Calls
  • How to Set Up Verified Caller ID (Use your number for Voice Calls)
  • How to Configure SMS Compliance Settings
  • Physical VoIP Deskphones (SIP)
  • LC Phone System - Error Code and Warning Dictionary
  • Why You Can't Delete a Twilio Subaccount from the Bizura?
  • KYC Verification on Persona — Best Practices
  • Custom Dispositions for Voice Calls
  • Avoiding Call Loops when routing calls to Internal Phone Numbers
  • How to Reduce Inbound Spam Calls
  • How to use Custom CSS to hide the Twilio error banner
  • Setting up webhooks to receive incoming calls, messages and status updates for calls (for Twilio users)
  • Understanding Default Phone Preferences for New Sub-Accounts
  • How to Create and Use Call Scripts in Web & App Dialers
  • The Phone Dialer Overview
  • Moving Phone Numbers: Migration Guide
  • 5% Stripe Markup Removed From All Phone System Charges
  • Call Events Not Working for Twilio

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