> ## Documentation Index > Fetch the complete documentation index at: https://www.vobiz.ai/docs/llms.txt > Use this file to discover all available pages before exploring further. # What Is SMS Marketing? How It Works, Best Practices & India Rules > SMS marketing sends promotional and transactional text messages to mobile numbers at scale — open rates above 90%, delivery in seconds, no app required. How bulk SMS campaigns work, DLT registration in India, opt-out compliance, and how to send with Vobiz SMS API. *November 2026 · Vobiz Team* **SMS marketing is the direct line to your customer's pocket — a text message that arrives in seconds, gets read within 3 minutes, and requires no app, no internet, and no algorithm to reach them.** At 90–98% open rates, SMS outperforms every other marketing channel. Done right — with proper consent, relevant content, and regulatory compliance — it's one of the highest-ROI channels available. > [!NOTE] > > **Key takeaways** > > * SMS open rate is 90–98% vs 20–25% for email — messages are read within minutes > * India requires DLT registration before sending any commercial SMS — no exceptions > * Promotional SMS goes to opted-in numbers only; transactional SMS can go to all numbers > * Sending hours: 9am–9pm only (TRAI rule); no Sunday/holiday promotional SMS > * Vobiz SMS API handles bulk sending, DLT-compliant templates, delivery reports, and opt-out management ## Promotional vs Transactional SMS The fundamental distinction in Indian SMS marketing: | Type | Content | DND Numbers | Hours | DLT Required | | - | - | - | - | - | | **Promotional** | Offers, discounts, campaigns | ❌ Blocked | 9am–9pm | ✅ Yes | | **Transactional** | OTP, order status, receipts | ✅ Allowed | Any time | ✅ Yes | | **Service/Implicit** | Account alerts, appointment reminders | ✅ Allowed | Any time | ✅ Yes | The misclassification risk: labelling a promotional message as transactional to bypass DND filters. TRAI audits for this — penalties include number blacklisting and fines. Use the correct category for your content. ## Why SMS Marketing Works **Immediacy**: SMS delivers in under 10 seconds to any mobile phone, anywhere in India, regardless of internet connectivity. **Reach**: 100% of mobile numbers receive SMS — no smartphone required, no app to install. **Open rate**: 90–98% of SMS messages are opened, almost all within 3 minutes of receipt. Email open rates average 20–25%. **Click-through rate**: SMS links achieve 10–30% CTR vs 2–5% for email. **Cost efficiency**: At ₹0.10–0.20 per message, reaching 10,000 customers costs ₹1,000–2,000 — less than a single Google Ads click for competitive keywords. **No algorithm**: Unlike social media or email, SMS is not subject to inbox filtering or platform algorithm changes. If you have a valid number and permission, your message gets through. ## India SMS Marketing Regulations (TRAI) India has some of the world's most structured SMS regulations. Non-compliance doesn't just risk penalties — it results in messages being blocked at the carrier level. ### DLT Registration (Mandatory) TRAI's Distributed Ledger Technology platform requires: 1. **Entity registration**: Your business must register as a principal entity on the DLT platform (Vodafone Idea, Jio, Airtel, BSNL, or TRAI-authorised operators). One-time process, usually free. 2. **Header registration**: Your SMS sender ID (e.g., `VOBIZ`, `ACMECR`) must be registered. Business SMS cannot use a 10-digit mobile number as sender ID. 3. **Template registration**: Every SMS template you send must be pre-approved. The template text must match what you actually send — only variables (name, amount, OTP) can differ. Unregistered SMS or unregistered templates are **blocked by all Indian carriers**. No exceptions. See the [DLT registration guide](https://www.vobiz.ai/docs/best-practices/dlt-registration.md). ### NDNC / DND Rules The National Do Not Call registry (also called DND) blocks promotional SMS to opted-out numbers. TRAI mandates: * Scrub your contact list against NDNC before every promotional campaign * Do not send promotional SMS to DND-registered numbers * Provide an opt-out mechanism in every promotional message (reply STOP) ### Sending Hours and Days | Message Type | Allowed Hours | Days | | - | - | - | | Promotional | 9am – 9pm | All days | | Transactional | Any time | Any day | Sending promotional SMS outside these windows results in carrier-level blocking and TRAI complaints. ## SMS Marketing Campaign Types **Promotional campaigns** Flash sales, seasonal offers, product launches, event invitations. Best practices: * Keep it under 160 characters (one SMS) * Include a clear call to action with a short link * Personalise with the customer's name when available * Send at optimal times: 11am–1pm and 6pm–8pm show highest engagement Example: ``` Hi [Name], FLAT 30% OFF sitewide today only! Shop now: vobiz.ai/sale | Reply STOP to opt out ``` **Transactional alerts** OTPs, order confirmations, shipping updates, payment receipts. These are expected by customers — high open rate is guaranteed. Example: ``` Your OTP for login to [App]: 847291. Valid for 10 minutes. Do not share. ``` **Appointment reminders** Reduce no-shows by 30–50% with a reminder 24 hours and 1 hour before the appointment. Example: ``` Reminder: Your appointment at [Clinic] is tomorrow at 10:30am with Dr. Sharma. Reply 1 to confirm, 2 to reschedule. ``` **Payment reminders** EMI due dates, invoice reminders, subscription renewals. Effective alternative to calling for smaller amounts. **Customer feedback / NPS** Post-purchase survey with a short link. Response rates are 2–3× higher than email surveys. **Winback campaigns** Re-engage inactive customers with a time-limited offer after a defined period of inactivity. ## Sending SMS with the Vobiz API Vobiz provides a programmable SMS API for sending individual and bulk messages with delivery receipts and opt-out management. **Send a single SMS:** ```bash theme={null} curl -X POST https://api.vobiz.ai/v1/sms/messages \ -H "X-Auth-Token: YOUR_AUTH_TOKEN" \ -H "Content-Type: application/json" \ -d '{ "from": "VOBIZ", "to": "+919876543210", "text": "Your order #12345 has been shipped. Track: vobiz.ai/track/12345", "type": "transactional", "dlt_template_id": "1234567890123456789" }' ``` **Send a bulk broadcast:** Use Vobiz's [broadcast API](https://www.vobiz.ai/docs/sms/api/broadcasts/create-broadcast.md) to upload a recipient list, preview the campaign, and schedule delivery. The API handles: * NDNC filtering (automatic DND scrub on promotional campaigns) * Delivery reports per message * Opt-out tracking (STOP replies automatically added to suppression list) * Template variable substitution (\[Name], \[Amount], \[OTP]) **Track delivery:** Every sent message returns a `messageUuid`. Poll the [message status endpoint](https://www.vobiz.ai/docs/sms/api/messages/get-message.md) or receive real-time delivery webhooks. ## SMS Marketing Best Practices **1. Get explicit consent**: For promotional SMS, capture consent at signup, purchase, or via keyword opt-in ("Text JOIN to 56789"). Keep consent records. **2. Personalise**: Even just the first name increases response rates by 15–20%. Pull data from your CRM at send time. **3. Time your sends**: Avoid Monday mornings and Friday evenings. Best windows: Tuesday–Thursday, 11am–1pm and 6–8pm. **4. Keep it short**: One SMS = 160 characters. Longer messages split into multiple parts and cost more. Write tightly. **5. Clear CTA**: One action per message. "Shop now", "Confirm your appointment", "Track your order" — not all three. **6. Easy opt-out**: Every promotional message must include "Reply STOP to opt out". Vobiz handles STOP responses automatically. **7. Test before sending**: Send to a test group of 100 numbers before the full send. Check rendering, link tracking, and delivery rate. **8. Measure**: Track delivery rate (aim > 95%), open rate (use link tracking), and conversion rate (UTM parameters on links). ## SMS vs WhatsApp vs Email | Channel | Open Rate | Delivery | App Required | Cost | Best for | | - | - | - | - | - | - | | **SMS** | 90–98% | Seconds, any phone | No | ₹0.10–0.25/msg | Time-sensitive, wide reach | | **WhatsApp** | 70–85% | Seconds | Yes (WhatsApp) | ₹0.50–1.50/msg | Rich media, two-way | | **Email** | 20–25% | Seconds to minutes | No | ₹0.01–0.05/email | Long content, low cost | SMS wins on reach and urgency. WhatsApp wins on richness and engagement for opted-in users. Email wins on cost for lower-urgency content. ## Next Steps * [Read the DLT registration guide](https://www.vobiz.ai/docs/best-practices/dlt-registration.md) — mandatory before sending in India * [Explore the Vobiz SMS API](https://www.vobiz.ai/docs/sms/overview.md) — bulk sending, delivery reports, opt-outs * [Set up RCS messaging](https://www.vobiz.ai/docs/blogs/what-is-rcs-messaging.md) for rich media campaigns on Android * [Read the WhatsApp marketing guide](https://www.vobiz.ai/docs/blogs/whatsapp-marketing-guide.md) for richer customer journeys * [Try the SMS API quickstart](https://www.vobiz.ai/docs/sms/quickstart.md) to send your first message This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.