OTP SMS Best Practices in India Delivery, Security & Compliance Tips

❌ Technical Reasons

• Unregistered DLT template
• Wrong sender ID category
• Gateway congestion during peak hours
• Single route without failover
• Mismatched template variables

❌ Compliance Reasons

• Promotional route used for OTP
• DND filtering on number
• Sender ID not mapped to entity
• Template not approved as Transactional
• Exceeding message rate limits

Always Use Transactional Route — Never Promotional

OTP messages must be sent via the Transactional SMS route, not Promotional. Transactional routes bypass DND (Do Not Disturb) filters and are available 24x7. Promotional routes are blocked for DND numbers and restricted between 9PM–9AM. Using the wrong route is the #1 cause of OTP delivery failure.

Register Your OTP Template on DLT as "Transactional"

On the DLT portal, register your OTP template under the Transactional category. Use {#var#} for the OTP number. Example of a correct template:

Use Multi-Route Failover for Maximum Delivery

Never rely on a single SMS route for OTP delivery. A good SMS gateway like InfyReach Connect provides smart multi-route failover — if Route A fails or is congested, the message automatically falls over to Route B within milliseconds. This is critical for OTP where delivery within 30–60 seconds is expected by users.

Keep OTP Messages Short and Clear

OTP messages should be concise. Include: the OTP, what it's for, expiry time, and a security warning. Avoid promotional language — it can trigger spam filters and confuse users. Keep the message under 160 characters to avoid multi-part SMS charges.

Implement OTP Fraud Prevention at Application Level

OTP fraud is a real problem in India. Protect your users with these application-level controls:

• Rate limiting — Max 3–5 OTP requests per number per hour
• OTP expiry — Keep OTP validity to 5–10 minutes maximum
• Attempt limits — Lock account after 3–5 wrong OTP attempts
• IP monitoring — Flag unusual request patterns from single IPs
• 6-digit OTPs — Use 6 digits instead of 4 for stronger security

Monitor DLR (Delivery Reports) in Real Time

Always integrate DLR webhooks from your SMS gateway into your application. Real-time delivery reports tell you exactly whether the OTP was delivered, failed, or is pending. This lets you trigger automatic resend logic or alert users to check their number — improving user experience significantly.

Choose a Gateway with Direct Operator Connectivity

Not all SMS gateways are equal. For OTP, you need a gateway with direct telecom operator connectivity (SMPP or API-level) — not one relying on multiple resellers. Direct connectivity means fewer hops, faster delivery, and higher DLR accuracy. InfyReach Connect provides direct SMPP and REST API connectivity for OTP-grade delivery in Mumbai and pan-India.