Glossary · CRM & retentionTOFU
DLT (Distributed Ledger Technology) for SMS
The short answer
DLT refers to the blockchain-based registration system mandated by TRAI for commercial SMS in India. Businesses must register as a principal entity, register their sender IDs (headers) and pre-register every message template before sending.
Messages that don't match a registered template exactly are typically blocked — which is why DLT problems are the most common cause of SMS delivery failure.
What needs registering
- Principal entity — your business
- Headers — the sender IDs recipients see
- Content templates — including variable placeholders
- Consent templates — for promotional messaging
In practice
Keep a shared document of every registered template with its exact wording and variables. Most delivery failures come from someone editing a message slightly — adding a word or emoji — without re-registering it. Transactional and promotional templates also need to use the correct header and category.
DLT message categories
| Category | Typical use |
|---|---|
| Transactional | OTPs from banks and similar critical messages |
| Service implicit | Order updates, account alerts linked to a transaction |
| Service explicit | Messages requiring explicit consent |
| Promotional | Offers and marketing, subject to DND preferences and time windows |
See SMS marketing.
DLT in practice
A business registers as an entity on a telecom operator's DLT platform, registers its sender IDs and message templates, and records customer consent before sending promotional SMS in India.
DLT steps
- Register the business entity
- Register sender IDs (headers)
- Register message templates
- Manage consent where required
Common DLT mistakes
- Sending messages that don't match registered templates
- Unregistered sender IDs
- Promotional messages without valid consent
Frequently asked questions
Does DLT apply to WhatsApp?
No — DLT covers SMS. WhatsApp has its own template approval and opt-in rules through Meta.
Why are our SMS failing after DLT registration?
Usually a mismatch between the sent message and the registered template, or a header used for the wrong category.
How long does DLT registration take?
Typically a few working days for entity and header approval; templates can be approved faster once the entity is active.
Do variables need to be marked in templates?
Yes — variable fields must be declared, and sent messages must match the template structure.
Is DLT registration mandatory for SMS in India?
Yes — commercial SMS senders in India must register under TRAI's DLT framework.
What happens if SMS doesn't match a DLT template?
Messages can be blocked by telecom operators.
Related terms
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