What is A2P Messaging?
A2P (Application-to-Person) messaging refers to any SMS sent from a business application to a consumer's mobile phone. This includes:
- Transactional messages — Order confirmations, shipping updates, appointment reminders
- Authentication — One-time passwords (OTPs), verification codes, 2FA
- Notifications — Account alerts, system updates, service notifications
- Marketing — Promotional messages, offers, campaigns
- Customer service — Support responses, ticket updates
The key characteristic of A2P is that messages originate from software or a business system, not from a person typing on their phone. Even if a human triggers the message (clicking "send notification"), it's still A2P because it's sent through an application.
What is P2P Messaging?
P2P (Person-to-Person) messaging is standard text messaging between individuals. When you text a friend or family member from your phone, that's P2P. Key characteristics:
- Sent manually by a person using their phone's messaging app
- Conversational and bi-directional
- Low volume (typical personal texting patterns)
- Not sent through business applications or APIs
Why the Distinction Matters
Carrier Requirements
US carriers (AT&T, Verizon, T-Mobile) strictly enforce the separation of A2P and P2P traffic. A2P traffic must be sent through registered channels:
- 10DLC — Registered long codes for most A2P messaging
- Short codes — 5-6 digit numbers for high-volume messaging
- Toll-free numbers — Verified toll-free for A2P (with registration)
Deliverability Impact
Sending A2P traffic through P2P channels results in:
- Filtering — Carriers detect and filter unregistered A2P traffic
- Blocking — Repeated violations lead to number blocking
- Low throughput — P2P channels have strict rate limits (1 msg/sec or less)
- Poor delivery rates — Many messages never reach recipients
Check your messaging compliance. Our API helps validate numbers and identify carriers before sending.
Message Provider API10DLC Registration for A2P
Since 2021, all US carriers require 10DLC registration for A2P messaging on standard phone numbers. The registration process involves:
- Brand registration — Register your business with The Campaign Registry
- Campaign registration — Register each message use case
- Vetting — Carriers verify your registration
- Number assignment — Associate numbers with approved campaigns
Read our complete 10DLC Registration Guide →
Common Mistakes
1. Treating A2P as P2P
Some businesses try to avoid 10DLC registration by sending through personal phone numbers or unregistered channels. This always fails — carriers detect A2P patterns and filter aggressively.
2. Using Personal Numbers for Business
Even if messages are "personal" in tone, sending them for business purposes makes them A2P. Customer outreach, lead follow-up, and appointment confirmations are all A2P regardless of sender.
3. Ignoring Volume Patterns
P2P channels have natural usage patterns. Sending 100+ messages per day from a single number triggers carrier filters, even without explicit A2P content.
Which Type Do You Need?
| Use Case | Type | Recommended Channel |
|---|---|---|
| Marketing campaigns | A2P | 10DLC or Short Code |
| Order confirmations | A2P | 10DLC or Toll-Free |
| 2FA/OTP codes | A2P | 10DLC, Short Code, or Toll-Free |
| Appointment reminders | A2P | 10DLC |
| Customer support responses | A2P | 10DLC |
| Personal conversations | P2P | Personal phone |
Frequently Asked Questions
Is SMS marketing A2P or P2P?
SMS marketing is always A2P (Application-to-Person). Any promotional messages sent from a business, regardless of how they're triggered, are considered A2P and require 10DLC registration in the US.
Can I send A2P messages without 10DLC?
Technically you can attempt to, but carriers will filter most messages and may block your numbers. Unregistered A2P traffic has very poor deliverability (often under 50%) and violates carrier terms. Short codes and verified toll-free numbers are alternatives to 10DLC.
What happens if I send A2P as P2P?
Carriers detect A2P patterns (volume, content, recipients) and will filter or block your messages. You'll see poor delivery rates, delayed messages, and eventually complete blocking of your numbers. This also violates carrier acceptable use policies.