---
title: What is CTA whitelisting, and why was my SMS blocked?
description: "If your SMS contains a link, an app link or a phone number for customers to call, that link or number must be **whitelisted** on the DLT portal where your business is registered. Messages carrying anything that isn't whitelisted are…"
url: "https://www.smsgatewaycenter.com/blog/kb/what-is-cta-whitelisting-and-why-was-my-sms-blocked/"
updated: "2026-09-18"
category: Bulk SMS / DLT / CTA Whitelisting
---

# What is CTA whitelisting, and why was my SMS blocked?

If your SMS contains a link, an app link or a phone number for customers to call, that link or number must be **whitelisted** on the DLT portal where your business is registered. Messages carrying anything that isn't whitelisted are blocked by the telecom operators and never reach the customer.

These links and numbers are called **CTAs (calls to action)**. There are four types:

- **URLs**: website links, including short links.
- **APKs**: Android app download links.
- **OTT links**: links that open apps or platforms, such as WhatsApp links.
- **Callback numbers**: mobile, landline or toll-free numbers you ask customers to call.

## Why this rule exists

TRAI issued the direction on 20 August 2024 to stop SMS being used to spread phishing links and malicious apps. Operators have blocked messages with non-whitelisted URLs, APKs and OTT links since 1 October 2024. The February 2025 amendment to TRAI's commercial communication rules extended the same scrubbing to callback numbers.

## How to tell if this is your problem

- Your delivery report shows **CTA Mismatch** for the failed messages.
- Messages *without* a link or number go through, but messages with one fail.
- You recently changed a landing page, short-link domain, app link or support number.

## What to do

1. Whitelist every link domain and number you use on your DLT portal (see *How do I whitelist URLs, app links and callback numbers on my DLT portal?*).
2. Make sure the template's variables use the right tags, such as `{#url#}` for links and `{#cbn#}` for numbers.
3. Resend only to the numbers that failed.

**Official source:** [TRAI press release on URL/APK/OTT whitelisting (PIB)](https://www.pib.gov.in/PressReleaseIframePage.aspx?PRID=2058943); [TCCCPR (Second Amendment) Regulations, 12 Feb 2025](https://www.trai.gov.in/sites/default/files/2025-02/Regulation_12022025.pdf).

### More Related Articles

- [How do I fix a “CTA Mismatch” failure?](https://www.smsgatewaycenter.com/blog/kb/how-do-i-fix-a-cta-mismatch-failure/)
- [How do I whitelist URLs, app links and callback numbers on my DLT portal?](https://www.smsgatewaycenter.com/blog/kb/how-do-i-whitelist-urls-app-links-and-callback-numbers-on-my-dlt-portal/)

Found this useful?[Add as Preferred Source on Google](https://www.google.com/preferences/source?q=smsgatewaycenter.com)