To send business or bulk SMS in India, registration on the Airtel DLT platform is mandatory as per TRAI regulations, requiring businesses to submit specific documents and follow a detailed registration process on the Airtel website. The process includes providing personal and business information, verifying through OTP, and submitting necessary documents, all done under specific guidelines and restrictions to avoid service interruptions. After successful registration, businesses must also register message content templates for sending promotional messages, with the final approval process potentially taking up to two days.