A2P messaging

A2P messaging, short for application-to-person messaging, means the messages that a business's software sends to people's phones. The OTP from your bank, the delivery update from a courier and the sale offer from a shop are all A2P messages. Messages that people send each other are called P2P, person-to-person. Mobile operators check and price A2P messages separately from P2P messages.

Here is how it works in general. The business's software asks a messaging platform to send a message, through the platform's API, a defined way for one program to ask another to do a job. The platform passes the message to an aggregator, a company with direct connections to the operators. The operator checks the message and delivers it to the phone. A delivery report then goes back to the business, saying whether the message reached the phone.

In India, the checking is strict. Under TRAI's rules, every business must register itself on the operators' shared register, called the DLT platform. It also registers its sender names, called headers, and the exact wording of each message type, called a template, with blanks for the OTP or the amount. The operator compares every message with these records and blocks any message that does not match. Promotional messages are also not sent to numbers on the do-not-disturb list. An SMS firewall at the operator blocks business messages that arrive by unofficial routes, such as messages pushed through ordinary SIM cards to avoid the A2P price. The business pays for each message it sends.

Take, for example, an OTP for logging in to an app. OTP verification sends it as a registered template and expects it to reach the phone within seconds.

Consider a courier company that sends delivery updates on WhatsApp. It uses the WhatsApp Business API, and pays for business messages under WhatsApp's own pricing.

Say an online shop plans messages for a festival sale. Journey orchestration decides who receives which message, and the shop sends them as promotional messages, which are treated differently from OTPs and alerts.

How is A2P different from P2P? A P2P message is usually covered by a person's mobile plan. An A2P message comes from one sender to millions of people, so the operator checks the sender, filters for spam and charges the business. Most businesses do not deal with each operator themselves. They send through messaging and voice APIs or an A2P SMS aggregator.