Before you send your first message through the API, three things need to be in place. You need a Relayion account, an Android device with an active SIM, and the Relayion app installed and running on that device. This guide walks through each step from registration to a live outbound message.
You will need an Android phone running Android 8 or later, a SIM card with SMS capability, and a stable internet connection on the device. The phone does not need to be new. A spare or dedicated device works well and is often the right call since the phone will be mounted in a fixed location and running continuously.
Step 1. Create your account
Go to relayion.com/register and fill in your name, email address, and a password. After submitting, check your inbox for a verification email and click the link inside. This activates your account and unlocks the console.
Step 2. Log in to the console
Once your email is verified, sign in at the Relayion Console. This is where you manage devices, generate API keys, configure webhooks, and monitor message activity. Keep it open. You will need it through the next steps.
Step 3. Add a device
In the console, navigate to Devices and click Add device. A pairing code and app download link are generated immediately. Keep this screen open. You will use both in the next two steps.
Step 4. Install the Relayion app
On your Android phone, scan the QR code shown in the console or open the download link directly. Install the Relayion app, then open it and tap Begin setup to proceed.
Step 5. Pair the device
In the app, tap Pair device and enter the 6-character pairing code shown in the console. The app sends this code to the Relayion backend, which links the physical phone to your account. Once paired, the setup wizard continues automatically to the permission steps.
Step 6. Grant permissions
The setup wizard walks through six permissions in sequence. Send SMS and Receive SMS are the core permissions that allow the app to relay outbound and receive inbound messages. Read phone state identifies which SIM slot to use on dual-SIM devices. Post notifications (Android 13 and later) allows the service to display its running status. Background activity prevents the operating system from suspending the app when the screen is off. Default SMS app is required on some Android versions for reliable inbound message delivery.
Each step can be skipped during setup and granted later from the Settings screen, but skipping any permission will prevent the corresponding function from working. The app will flag missing permissions on the dashboard so you know exactly what needs attention. The app does not access your contacts, camera, or any data unrelated to SMS dispatch.
Step 7. Start the service
After the permission wizard completes, the app takes you to the dashboard. Tap Start service. You will see a persistent notification in your phone's status bar confirming the service is running. The relay service stays active in the background and is ready to dispatch messages as requests arrive.
Plug the phone into a charger and place it somewhere with a stable connection. A desk mount, shelf, or server room works well. Treat it like a piece of infrastructure. It needs to stay powered and online to relay messages reliably.
Step 8. Send a test message from the console
With the service running, go back to the console and use the Test SMS feature on your device. Enter a phone number you can verify, write a short message, and send it. If everything is connected correctly, the message will arrive within seconds and the console will show the delivery status update to Sent.
If the test message does not arrive, check that the service is still running in the app, the device shows as online in the console, and the SIM has SMS capability on the current carrier plan.
Step 9. Create an API key
In the console, navigate to API Keys and create a new key. Each key is permanently bound to a specific device and SIM slot at creation time. When your application sends a request using that key, Relayion routes it to the correct device automatically. No device ID is required in the request body.
Copy the key and store it securely. It will not be shown again. From here, sending a message is a single HTTP POST to /api/v1/outbound. The API reference covers the full request format, response envelope, status progression, and error codes.
Step 10. Set up a webhook
If your application needs to receive replies or track delivery status in real time, configure a webhook URL in the console. Relayion will POST an event payload to that URL whenever a message is received, dispatched, delivered, or fails.
The webhooks section of the docs covers all six event types and includes a Node.js example for verifying the HMAC-SHA256 signature on incoming payloads. Signature verification is required in production. It ensures the payloads your server receives are genuinely from Relayion and have not been tampered with in transit.
That covers the full setup. One device, one SIM, one API key, and a webhook endpoint for inbound. Everything your application needs to send and receive messages is now in place.