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DLT Scrubbing

The real-time check an Indian operator runs on each commercial SMS against its registered header, template, consent, DND and delivery chain.

Also called: SMS scrubbing · DLT scrubbing function · Operator scrubbing · DLT rejection

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Follow 2 lakh SMS through the scrubber

7 / 7

  2. 0.7% drop-off · 1,400 SMS lost

  3. 13.7% drop-off · 27,200 SMS lost

  4. 0.29% drop-off · 500 SMS lost

  5. 7.4% drop-off · 12,700 SMS lost

  6. 17% drop-off · 26,900 SMS lost(biggest leak)

  7. 5% drop-off · 6,600 SMS lost

Stage 7 of 7

Delivered to handsets

1,24,700 SMS

95% of the previous stage made it here (5% drop-off, 6,600 SMS lost). That is 62.4% of the top.

The rest failed at the handset: switched off, out of coverage or no longer in service.

Top to bottom
62.4%
Biggest leak
Links whitelisted → NCPR preference allows it (17%)
An illustrative promotional send, check by check. Step through each stage to see how many messages it removed and why; the biggest leak is flagged.

Stage 7 of 7: Delivered to handsets, 1,24,700 SMS. 95% of the previous stage made it here (5% drop-off, 6,600 SMS lost). That is 62.4% of the top. The rest failed at the handset: switched off, out of coverage or no longer in service.

01What is DLT scrubbing?

DLT scrubbing is the real-time check that an Indian access provider runs on every commercial SMS before delivering it. Under TRAI's TCCCPR framework, a business (the principal entity) first completes DLT Registration of its entity, headers and content templates on an operator's Distributed Ledger Technology (DLT) platform. Scrubbing is the enforcement step that follows: each message is compared with what was registered, and anything that does not match is dropped before it reaches a handset.

The checks follow the same logic on every network, even if the order varies. Is the DLT Header registered, active and owned by the principal entity named on the message? Does the text match a DLT Content Template linked to that header, with only the {#var#} placeholders varying? Does the declared PE-TM Chain Binding (the chain of telemarketers carrying the message) match what was registered? For promotional traffic, does the recipient's preference in the DND Registry (NCPR) allow this category? For service-explicit traffic, is there a valid consent record? And, since 1 October 2024, is every URL, APK or OTT link in the text whitelisted?

Scrubbing is neither registration nor a delivery report. Registration happens once, on a portal; scrubbing happens on every send, inside the operator's network. An SMS Delivery Report says whether a handset received a message, whereas a scrubbing rejection means the message was never sent to the handset at all. Rejections usually reach the sender as a failed DLR carrying an operator- or aggregator-specific error code, which is why mapping those codes to causes is the first job when a campaign under-delivers.

Key takeaways

  • DLT scrubbing is the operator-side check every commercial SMS in India passes before delivery: header, template, chain, links, consent and preferences.
  • A message that fails any check is dropped, not queued, so one edited word in fixed template text can block a whole campaign.
  • Since 1 October 2024, SMS carrying URLs, APK or OTT links that are not whitelisted fail scrubbing.
  • Promotional SMS is checked against the recipient's DND preference; service-explicit SMS needs a recorded consent instead.
  • Rejections come back as failed delivery reports with operator- or aggregator-specific codes, so map codes to causes before retrying.

02 · How it works, step by step

How does DLT scrubbing work?

  1. Step 1

    The message goes out with its DLT identifiers

    Your application or aggregator submits the SMS with the principal entity ID, the header, the registered content template ID and the telemarketer chain details, as SMPP optional parameters or as fields your aggregator's API defines.

  2. Step 2

    Header and entity check

    The DLT platform of the operator the traffic enters confirms that the header is registered, active, mapped to that principal entity and of the right type for the message category.

  3. Step 3

    Template match

    The text is compared with the template registered under that ID and header. Fixed text must match exactly, including spaces and punctuation; only the {#var#} positions may differ, within their length limit.

  4. Step 4

    Chain and link checks

    The declared PE-TM chain must match the registered binding, and every URL, APK or OTT link in the text must be on the entity's whitelist.

  5. Step 5

    Preference and consent check

    Promotional messages are scrubbed against the recipient's NCPR preference and the sending-hour rules; service-explicit messages need a valid consent record; transactional and service-implicit messages skip the DND check.

  6. Step 6

    Deliver or drop

    Messages that pass go on to the terminating network. Those that fail are dropped and reported back as a failed delivery report with a rejection code.

03DLT scrubbing: key facts and limits

Where it runs
On the operator's DLT platform, for every commercial SMS
Legal basis
TRAI TCCCPR 2018 and its amendments
Checked against
Header, content template, PE-TM chain, links, consent, NCPR preference
Link rule
Non-whitelisted URLs, APK and OTT links blocked since 1 October 2024
Chain enforcement
Undeclared PE-TM chains rejected since 11 December 2024
Template variables
{#var#} placeholders; fixed text must match exactly
Failure signal
Failed delivery report with a provider-specific error code

04Example: A Pune lender's festive send that half-failed

A Pune consumer-finance company sends a promotional SMS to 2 lakh customers and sees only about 62% delivered. The failed delivery reports group into three causes. A copywriter changed "valid till" to "valid until" in the fixed text, so one segment failed the template match. A new click-tracking short domain had never been whitelisted, so another segment failed the link check. The rest were customers whose DND preference blocks this category, an expected loss rather than an error. The team re-registers the edited wording as a new template, whitelists its own branded short domain, adds a pre-send template check to its sending service and resends the two failed segments the next morning (figures illustrative).

05DLT scrubbing in code

// Check rendered text against the registered DLT template before submitting.
// Fixed text must match exactly; each {#var#} may hold up to MAX_VAR characters.
const MAX_VAR = 30; // a common per-variable limit: confirm your DLT platform's rule
 
function templateToRegex(template) {
  const parts = template.split("{#var#}").map((s) => s.replace(/[.*+?^${}()|[\]\\]/g, "\\$&"));
  return new RegExp("^" + parts.join(`[\\s\\S]{0,${MAX_VAR}}`) + "$");
}
 
const registered = {
  id: "1107160000000000000", // DLT content template ID (illustrative)
  text: "Dear {#var#}, your EMI of Rs.{#var#} is due on {#var#}. Pay at {#var#} - ABC Finance",
};
 
export function matchesTemplate(text, tpl = registered) {
  return templateToRegex(tpl.text).test(text);
}
 
matchesTemplate("Dear Asha, your EMI of Rs.4,250 is due on 05-Nov. Pay at https://abcfin.in/p/x7 - ABC Finance"); // true
matchesTemplate("Hi Asha, your EMI of Rs.4,250 is due on 05-Nov. Pay at https://abcfin.in/p/x7 - ABC Finance");   // false: fixed text changed

A local check catches template drift before the operator does. It cannot see the whitelist, consent or DND state, so the delivery report still has the final word.

06 · Common mistakes, and the fix

Common mistakes with DLT scrubbing

  • Editing fixed template text in code

    A changed word, an extra space or swapped punctuation outside a {#var#} breaks the match. Keep each template's text in one versioned place tied to its template ID, and run a test send after every edit.

  • Retrying scrubbing rejections

    A message rejected for its header, template or chain will be rejected again. Classify the failed DLR first; retry only handset-side failures, and fix the registration for the rest.

  • Putting offers in service templates

    Content that mixes a promotion into a service or transactional message is treated as promotional, so it meets the DND check and can be flagged as misuse. Register a promotional template for offers.

  • Adding links or routes after registration

    A new tracking domain or a new aggregator in the route must be whitelisted or added to the PE-TM chain before the first send, not after the rejections arrive.

  • Reading "submitted" as "sent"

    An HTTP 200 from your aggregator only means it accepted the message. Track the delivery report per message to see what scrubbing actually did.

07Why does DLT scrubbing matter?

For any business sending OTPs, order updates or offers by SMS in India, scrubbing decides what actually leaves the network. A template edited by one character, a header that lapsed, a new tracking domain nobody whitelisted or an undeclared aggregator in the route will quietly zero out a send while your application logs "submitted". Teams that understand scrubbing read the failed DLR, fix the right registration and resend within the hour; teams that don't blame the network, retry blindly and pay for messages that were never going to pass.

08 · Tips from the bench

Best practices for DLT scrubbing

  • Keep a table mapping your aggregator's rejection codes to causes, and alert when one cause passes a threshold.
  • Validate rendered text against the registered template in your own code before submitting.
  • Use one template per purpose; templates stuffed with variables are harder to match and more likely to be refused.
  • Whitelist a branded short domain once and reuse it across templates.

09DLT Scrubbing FAQs

Why is my DLT SMS failing with a template mismatch?+
Because the text you sent differs from the registered template outside its {#var#} placeholders. Common causes are edited fixed words, extra spaces or line breaks, a variable longer than the platform allows, or a template sent under a header it isn't linked to.
Does DLT scrubbing block OTP messages to DND numbers?+
No. DND preferences apply to promotional messages. OTPs and other transactional or service-implicit messages are not checked against NCPR, though they must still match a registered header and template and pass the link check.
Am I charged for SMS rejected in DLT scrubbing?+
That depends on your provider's contract. Some aggregators bill on submission and others on delivery, so check whether rejected messages are billable and reconcile invoices against delivery reports.
How is DLT scrubbing different from DLT registration?+
Registration is the one-time setup of your entity, headers, templates and chain on a DLT portal; scrubbing enforces those records on every message. You can be fully registered and still fail scrubbing when a message drifts from what you registered.
Can scrubbing reject a message because of the telemarketer chain?+
Yes. Under TRAI's traceability rules each message must travel along a PE-TM chain that matches the binding registered on DLT. After the declaration deadline was extended to 10 December 2024, operators have rejected traffic through any undeclared hop since 11 December 2024.

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