Why Your SMS Delivery Rate Is Low & How to Fix It

Bulk SMS campaigns are powerful — but only if your messages actually get delivered. Many businesses struggle with a low SMS delivery rate, which affects customer communication, OTP verification, marketing campaigns, and transactional updates.

A poor delivery rate means your messages are getting blocked, filtered, or failing due to technical or regulatory issues. In this guide, you’ll learn the major reasons behind low delivery and practical steps to fix them.

What Is SMS Delivery Rate?

SMS Delivery Rate = (Delivered Messages / Total Messages Sent) × 100

A healthy delivery rate is usually 95–98%.
Anything below 90% signals a serious problem.

Top Reasons Your SMS Delivery Rate Is Low

1. DLT Failures (India-Specific Issue)

Since DLT is mandatory, even small issues can block your SMS completely.

Common DLT Issues

• Wrong or inactive sender ID

• Unapproved SMS templates

• Incorrect template header & body mapping

• Missing variables or mismatched characters

Fix

• Ensure all templates are approved

• Map sender ID & template correctly

• Use exact template text (even punctuation matters)

2. Poor Sender ID Configuration

If your sender ID is invalid, expired, or not registered, telecom operators automatically block messages.

Fix

• Register sender ID properly on DLT

• Use fixed & verified sender IDs

• Avoid changing sender ID frequently

3. Sending SMS to Non-Active or Switch-Off Numbers

Mobile numbers that are:

• Switched off

• Out of network

• Invalid

• Ported recently

…will cause delivery failures.

Fix

• Clean your database regularly

• Remove inactive or unreachable numbers

• Use HLR (Home Location Register) lookup tools

4. Network Congestion or Operator Filters

Telecom operators may block or delay messages during:

• Festivals

• Peak hours

• System maintenance

• Congested network zones

Fix

• Schedule SMS during low-traffic hours

• Split bulk campaigns into batches

• Use multi-operator routing

5. Content Violations (Filtered by Operators)

Certain words or content styles trigger spam filters.

Blocked Examples

• Excessive caps

• Adult terms

• High-frequency promotional words

• Scam-like keywords

Fix

• Use clean, professional content

• Avoid sensitive keywords

• Keep SMS short & compliant

6. Overuse of URL Shorteners

Spam filters often block SMS that contain unknown or suspicious shortened links.

Fix

• Use branded URLs or your domain

• Avoid free shorteners like bit.ly for bulk campaigns

7. Sending Messages to DND (Do Not Disturb) Numbers

Promotional SMS cannot be delivered to DND-registered users.

Fix

• Switch to transactional route for important alerts

• Use WhatsApp for promotional communication

8. Low-Quality SMS Gateway Provider

Cheap SMS services often use poor routing which lowers delivery rate.

Fix

• Choose a reliable provider with:
  ✔ Direct operator routes
  ✔ DLR (Delivery Report) accuracy
  ✔ High throughput
  ✔ Redundant routing

Common SMS Delivery Issues & Fixes (Table)

How to Improve Your SMS Delivery Rate (Checklist)

✔ Use DLT-approved templates

✔ Clean your phone number database monthly

✔ Avoid spam words

✔ Use branded links instead of free shorteners

✔ Choose a high-quality bulk SMS provider

✔ Personalize the message for higher engagement

✔ Send messages during optimal times

✔ Use real-time delivery tracking reports (DLR)

Ideal SMS Delivery Benchmarks

Conclusion

Low SMS delivery rate affects everything — lead generation, OTP verification, customer support, payments, and conversions. By fixing DLT issues, improving content quality, using verified sender IDs, and choosing a reliable SMS provider, you can achieve 95–98% delivery consistently.