Glossary · Messaging
A2P SMS
In one sentence
A2P (application-to-person) SMS is a text message sent automatically by software to a mobile user, such as a one-time passcode, delivery update, appointment reminder or marketing offer, through a messaging platform connected to mobile networks.
Also known as : A2P SMS · A2P messaging · application-to-person SMS · business SMS · transactional SMS · bulk SMS
What is A2P SMS?
When your bank texts a code to approve a payment, or your dentist reminds you about tomorrow’s check-up, nobody at the company typed that message. Software generated it and handed it to a platform that delivered it through the mobile networks. That is A2P SMS: application-to-person.
The opposite is P2P, the texts people send each other. The distinction matters commercially as well as technically. Networks charge for A2P traffic differently, filter bulk messages disguised as personal texts and set rules on sender IDs and content.
A2P traffic usually falls into three groups:
- codes and alerts: two-factor authentication, fraud warnings;
- transactional messages: order confirmations, delivery slots, appointment reminders;
- marketing messages: offers and win-back campaigns, covered by direct marketing rules.
How it works
- Your application (CRM, booking system, online shop) calls a provider’s telecom API with the recipient’s number and the text.
- The platform applies the sender: an alphanumeric name, a short code or a long virtual number.
- It routes the message to the recipient’s network, which delivers it to the handset.
- A delivery receipt comes back to your application, often by webhook, so you know whether it arrived.
A standard SMS holds 160 characters. Longer messages, or those using characters outside the GSM alphabet such as most emojis, are split into segments that are each counted separately.
In the UK, people can forward spam texts free to 7726, which networks use to block abusive senders. Marketing texts fall under PECR and UK GDPR, enforced by the ICO; see GDPR and telephony. In Ireland the Data Protection Commission applies equivalent e-privacy rules.
Example
A chain of physiotherapy clinics in Dublin loses appointments to no-shows. Its booking software now sends an A2P text 24 hours before each session, from the sender ID “PHYSIO” with a link to rebook. Because the sender is alphanumeric, the message also gives the clinic’s phone number for anyone who wants to talk. Reception spends less time ringing patients to confirm, and freed slots are offered to the waiting list.
A2P SMS at Universal Telecom
Universal Telecom developer APIs let you build messaging and calling into your own tools. For two-way conversations with customers rather than notifications, the WhatsApp Business API is often a better fit, with pre-approved message templates. Before any marketing campaign, check the consent you hold for each recipient.
Frequently asked questions
What is the difference between A2P and P2P SMS?
P2P (person-to-person) texts are sent between two people's phones. A2P texts come from software, usually in volume, through a platform connected to the networks. Networks price, filter and regulate the two kinds of traffic differently.
Do marketing texts need consent in the UK?
Generally yes. Under PECR, marketing texts to individuals need their prior consent, unless the 'soft opt-in' applies to existing customers who bought something similar and were given a chance to opt out. Every message must offer a simple way to opt out.
Can customers reply to an alphanumeric sender ID?
No. A sender ID such as 'DENTALCARE' is one-way. If you want replies, send from a long number or a short code instead.
Related terms
- Telecom API
A telecom API is a programming interface that lets software control communication services: place or receive calls, manage phone numbers, send SMS, pull call history or get notified in real time when something happens on a call.
- CPaaS
CPaaS (communications platform as a service) is a cloud service that provides communication building blocks, such as voice calls, SMS, WhatsApp, video and phone numbers, as APIs that developers embed in their own applications.
- WhatsApp Business API
The WhatsApp Business API is Meta's business access to WhatsApp. It connects a company number to software such as a CRM, helpdesk or phone system, so several people can answer customers and messages sit alongside other channels.
- TPS (Telephone Preference Service)
The Telephone Preference Service (TPS) is the UK's free opt-out register for unsolicited live sales and marketing calls. Under PECR, businesses must not make such calls to registered numbers unless the person has told that caller they are happy to be called.
- GDPR and telephony
GDPR applies to business telephony whenever it handles personal data: phone numbers, call logs, recordings and voicemails. It requires a defined purpose and lawful basis, clear information for callers and staff, limited retention and safeguards from suppliers.
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