Understanding TRAI Bulk SMS Regulations in India

1. What is Bulk SMS?
Bulk SMS (or A2P – Application-to-Person messaging) refers to sending large volumes of text messages—for marketing, notifications, alerts, or OTPs.

2. Categories of SMS
TRAI categorizes messages to protect users from spam and phishing:
Transactional (T): OTPs, account alerts—can be sent 24×7, even to DND numbers.
Service (S): Informational, non-promo updates (bill reminders, delivery).
Promotional (P): Marketing offers—allowed only 9 AM–9 PM and not to DND numbers.
Government (G): Official alerts (govt schemes, health advisories)

3. Sender Header & Template Registration
Every SMS header (sender ID) and template must be registered via DLT and approved by telecom providers
Headers will carry suffixes (‑P, ‑S, ‑T, ‑G) automatically from May 6, 2025, enhancing transparency

4. Whitelisting Links & Traceability
From October 1, 2024, all commercial messages containing URLs/APKs/OTT links must be whitelisted on DLT; unregistered links are blocked
Since December 2024, telecom operators must trace bulk OTPs/messages to senders to combat fraud, without impacting delivery speed


5. DND Scrubbing & Opt-In/Opt-Out
Promotional SMS must exclude DND‑registered numbers; opt-in consent is mandatory, opt‑out (e.g., “STOP”) must be provided
Valid opt-in expires after 180 days unless renewed

6. Time Limits & Messaging Throttling
Promotional SMS: Only between 9 AM–9 PM, 6 messages/hour per sender ID per recipient
Transactional/service types have no time restrictions.


7. Penalties & Enforcement
Non-compliance (e.g. sending to DND numbers, using wrong route, unregistered content/header): fines of ₹25,000–₹275,000 per offence, plus sender blacklisting for up to 2 years
Telcos must employ AI/ML tools to detect UCC and block misbehaving bulk senders
Complaints from 10+ users prompt immediate investigation and possible disconnection

💼 Real-World Impacts
Spam reduction: Since the May suffix rollout, users can easily distinguish message types; awareness campaigns by police are live
Link whitelist delays: Some institutions saw a 15–20% message drop until whitelisting was completed
Fewer phishing attacks: Traceability of OTPs helps curb smishing
Improved user trust & lower churn: Transparent headers and opt‑out options lead to cleaner subscriber lists.

🎯 Best Practices to Stay Ahead
Use trusted bulk SMS vendors with robust DLT integration.
Automate template registration and monitor header suffix compliance.
Maintain updated opt‑in records; send renewal reminders before 180‑day expiry.
Regularly check DND scrubbing, timing, message counts per user.
Track complaints and correlate them with your campaigns.
Audit content monthly; ensure no link/template drift.
Partner with providers offering AI/ML spam detection.

📌 Final Takeaway
TRAI’s evolving regulations—from header classification and link whitelisting to strict traceability—are reshaping the Bulk SMS landscape in India. By aligning with these rules, your organization can improve deliverability, build trust, and avoid hefty penalties.

Need a tailored compliance strategy, template examples, or help choosing a bulk-SMS partner? I’d be happy to assist!