DLT registration for bulk SMS in India: the complete plain-English guide
What DLT is, the four things you must register, why messages get scrubbed, and how long each step realistically takes.
Read guideFour channels, four genuinely different jobs. Most businesses use whichever one they bought first, then conclude the channel does not work. Here is how to choose deliberately.
Four questions that decide it
- How urgent is it? If the message loses value in ten minutes, only SMS is reliable enough.
- Can the recipient read comfortably? If literacy or script is a barrier, voice is not a nice-to-have, it is the only option.
- How rich does the content need to be? One sentence, or a catalogue with images?
- Does the customer need to reply? A broadcast that invites a reply and cannot receive one damages trust.
SMS — the universal baseline
SMS reaches every mobile phone in India. No app, no data pack, no login, no smartphone. Delivery is in seconds on priority routes, and read rates are extremely high because the notification is unavoidable.
Use it for: OTPs, payment alerts, dispatch notifications, appointment reminders, deadline-driven offers.
Limits: 160 characters, no images, no reply handling, and promotional traffic is confined to 9 AM – 9 PM and non-DND numbers. See transactional SMS and promotional SMS.
WhatsApp — the conversation channel
WhatsApp is where Indian customers already are, and it is the only channel on this list where a broadcast can become a genuine two-way conversation. You can send images, PDFs, location pins, product catalogues and tappable buttons, and the customer can ask a question and get an answer.
Use it for: order lifecycle updates, customer support, catalogue sharing, document delivery, appointment management, lead qualification.
Limits: requires a smartphone with WhatsApp installed, outbound messages must use Meta-approved templates, and pricing is per conversation by category. Unofficial bulk-sender tools get numbers banned — use the official Business API.
Voice — for audiences text cannot reach
A recorded voice message in the listener's own language reaches people who cannot read, do not read the script your message is written in, or simply respond better to a human voice. For rural, semi-urban, elderly and regional-language audiences this is not a fallback, it is the primary channel.
Use it for: announcements to member or beneficiary lists, festival greetings, price and procurement notices, awareness campaigns, collection reminders.
Two variants: voice SMS is one-way — the recipient listens and the call ends. Bulk voice call (OBD) adds keypad response, so "press 1 to speak to an executive" turns the broadcast into a qualified lead list.
Email — depth at the lowest cost
Email is the cheapest channel per contact at scale, has effectively no length limit, supports attachments and rich design, and gives you the most granular analytics. You also own the list outright.
Use it for: newsletters, dealer price lists and catalogues, invoices and statements, lead nurturing sequences, detailed post-purchase content.
Limits: lower and slower open rates than SMS or WhatsApp, and deliverability collapses without correct SPF, DKIM and DMARC records. See bulk email and email marketing.
A comparison you can act on
| Factor | SMS | Voice | ||
|---|---|---|---|---|
| Reach | Every handset | Smartphones | Every handset | Email users |
| Speed to read | Minutes | Minutes to hours | Immediate or missed | Hours to days |
| Rich content | No | Yes | Audio only | Yes |
| Two-way | No | Yes | Keypad only | Yes, slowly |
| Literacy needed | Yes | Yes | No | Yes |
| Cost per contact | Low | Medium | Medium | Lowest |
The combinations that outperform single channels
- SMS then WhatsApp. SMS guarantees the notification arrives; WhatsApp carries the detail and handles the reply.
- Missed call then SMS. Missed call alert captures the lead at zero cost to the customer; an instant SMS delivers the brochure link.
- Voice broadcast then OBD. Announce to everyone, then re-dial the people who listened all the way through and let them press 1.
- Email then SMS reminder. Email carries the invoice or catalogue; a short SMS nudges the people who did not open it.
The one rule that matters
Pick the channel from the job, not from what you already own. If you are unsure, describe the outcome you want to us — more enquiries, fewer support calls, faster payments — and we will name the channel and tell you when the cheaper option would do the same work.