DLT scrubbing is the check that compares your recipient list with each customer's registered preferences and consents before a commercial SMS is delivered. A message is blocked at scrubbing when the person has blocked that category, when you have no consent, or when the header, template or link does not match the records. Fix the cause, not the symptom.
By Rohit Jadhav. Last reviewed 25 October 2026. This is operational guidance, not legal advice. Reports and error labels differ by provider, so ask yours what each failure code means.
The campaign went out, the dashboard said "submitted", and then the numbers came in: a large share "failed" or "blocked by scrubbing". It is one of the most frustrating results in bulk SMS, because the message looked right. This guide explains what DLT scrubbing is, why messages get blocked and how to work out which cause applies to you. It is part of our main guide to DLT registration in India. For help with the set-up, Nexcomm's bulk SMS service includes template submission and compliance support. More guides sit under Compliance & Regulations.
What is DLT scrubbing?
TRAI's regulation defines scrubbing as the process of comparing the list of phone numbers a sender wants to message with the list in the preference register and the consent register, to check whether commercial communication can be sent to each recipient as per their registered preferences or consent. A registered scrubber does this. The scrubbing function also checks messages that contain URLs, APKs, OTT links or call-back numbers against whitelisted data uploaded by the sender, and it takes the customer's preferred time slots and types of days into account.
Why does scrubbing block a message?
| Cause | What it means | What to check |
|---|---|---|
| Category blocked | The recipient has opted out of that category, for example promotional | Your message category. See DND SMS rules |
| No consent | The recipient has blocked promotions and you have no consent on record | Your consent records. See SMS consent in India |
| Header or template mismatch | The message does not match a registered header and template | Header and template details |
| Link not whitelisted | The URL, APK or number is not on your whitelist | URL whitelisting |
| Time band or day type | The recipient allows delivery only in certain slots | Send time of the campaign |
| Content type mismatch | The content looks promotional but is registered as service | Category |
How can you find out which cause applies?
- Ask for the failure reason per number from your SMS provider, not just the count.
- Group the failures. If they cluster on the same few recipients, it is likely category or consent. If they affect every message with a link, it is the whitelist.
- Test one message to your own number with and without the link.
- Compare the sent text with the registered template character by character.
- Check the category of the template against its content.
- Fix and resend a small batch before the full list.
Can you remove the problem by cleaning your list?
Partly. You cannot override someone's block, but you can stop paying to message people who will not receive it. Build the list from people who gave you their number for this purpose, record consent, remove those who opted out and avoid bought lists. The regulation also says the scrubbing function reports probable instances of lists collected through harvesting software or dictionary attacks, so a list assembled that way is a risk, not a shortcut.
What are the consequences of ignoring scrubbing?
A blocked message is the mild outcome. The regulation also provides for action against senders found sending unsolicited commercial communications: for a first violation, outgoing services of all telecom resources allotted to the sender can be barred for fifteen days, and for repeated violations they can be disconnected for one year. These are serious, so treat repeated scrubbing failures on promotional campaigns as a warning. We cover the rules in what the TCCCPR says.
A worked example (hypothetical)
A real estate firm in Pune sends 20,000 promotional SMS about a new launch. This is an invented example. Its report shows 6,000 failures. The provider's breakdown says 4,500 are blocked because the recipients have blocked promotions and there is no consent on record, 900 are failed because the message contained an unregistered link and 600 are other delivery errors. The firm whitelists the link and resends those 900. For the 4,500 it cannot do anything, and it decides to collect consent through a sign-up form on its site for the next campaign, rather than buying another list.
Common mistakes with scrubbing
- Treating "submitted" as "delivered". Scrubbing happens after submission.
- Blaming the provider without reading the reasons. Ask for the breakdown.
- Re-sending the whole list. The blocked part will be blocked again.
- Using a purchased list. It has no consent and it fails scrubbing.
- Ignoring link registration. It is a separate step.
- Calling promotions service messages. It leads to rejections and warnings.
Frequently asked questions
What does "blocked by scrubbing" mean?
It means the message failed the check against the preference and consent registers, or against your registered header, template or links. Ask your provider for the specific reason per number.
Why do some numbers fail and others do not?
Because each customer has their own preferences. A person who has blocked promotional messages will not receive one unless you hold their consent. Others in the same list will.
Can I stop scrubbing from blocking my messages?
No. It is how the system enforces customers' choices. You can reduce failures by using consented lists, correct categories, matching templates and registered links.
Does scrubbing apply to OTP and service messages?
Scrubbing applies to commercial communication generally, but transactional and service messages are treated differently from promotional ones under the regulation. The check still matches headers, templates and links.
How long should I wait before treating a message as failed?
Ask your provider for its normal delivery window and the point at which a status becomes final. Do not resend repeatedly in the meantime, since duplicates annoy recipients.
Sources checked
All checked on 25 October 2026.
- TRAI, consolidated Telecom Commercial Communications Customer Preference Regulations, 2018 (definition and functions of scrubbing; whitelisted links; action against senders)
If your campaigns keep failing at scrubbing and you want a second opinion, you can reach our team through the contact page.