Short answer: Yes you can SMS to end-users in India without TRAI registration.
Long answer, is described below:
By default, when you send messages to recipients in India, Amazon SNS uses International Long Distance Operator (ILDO) connections to transmit those messages. When recipients see a message that's sent over an ILDO connection, it appears to be sent from a random numeric ID.
If you prefer to use an alphabetic sender ID for your SMS messages, you have to send those messages over local routes rather than ILDO routes. To send messages using local routes, you must first register your use case and message templates with the Telecom Regulatory Authority of India (TRAI) through Distributed Ledger Technology (DLT) portals. These registration requirements are designed to reduce the number of unsolicited messages that Indian consumers receive and to protect consumers from potentially harmful messages. This registration process is managed by Vodafone India through its Vilpower service.
The price for sending messages using ILDO connections is higher than the price for sending messages through local routes.
Lastly I enlist Special requirements for sending SMS messages to recipients in India for further reading and review.
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