SMSGate Setup Guide

SMSGate (also known as SMS Gateway for Android™) is a free, open-source app that turns any Android phone into a personal SMS gateway. Once installed on a phone that stays connected to the internet, Calendo can ask it to send SMS messages on your behalf — using your own phone number.

This means you pay nothing extra for SMS reminders. The messages are sent through your normal mobile plan, just as if you typed them yourself.

• No registration required — the app generates credentials automatically.
• End-to-end encryption — your message content is encrypted between Calendo and your phone.
• Open source — free to use, inspect, and trust.
• Works on any Android 5.0+ device.

The SMSGate app is not on the Google Play Store. You install it directly from the official documentation page at docs.sms-gate.app.

Prerequisites

• An Android device running Android 5.0 (Lollipop) or later.
• A SIM card with SMS capability.
• An internet connection on the device (mobile data or Wi-Fi).

Installation steps

1. On your Android device, open the browser and go to docs.sms-gate.app/installation/.
2. Follow the Installing from APK section on that page to download the latest APK release directly from the official GitHub releases page.
3. Before you can install it, you need to allow your device to install apps from unknown sources: go to Settings → Security (or Privacy on newer devices) and enable Install unknown apps (or Unknown sources).
4. Open the downloaded APK with your file manager and follow the on-screen prompts to install.
5. When the app opens for the first time, grant the requested permissions:
   • Send SMS — required to send messages.
   • Read Phone State — needed for SIM card selection if you have dual SIM.

After opening SMSGate for the first time you will see the main screen. There are two important toggles you need to turn on here:

• Cloud server — This connects your phone to the SMSGate cloud relay, which Calendo uses to reach your device. Make sure this toggle is enabled.
• Start on boot — This ensures the gateway restarts automatically whenever your phone reboots, so SMS reminders never stop working unexpectedly.

Tap the Settings (gear) icon in SMSGate to open the settings screen. Here you will find two important sections:

• Cloud server — Tap this to see your automatically generated Username and Password. You will need these in the next step.
• Encryption — This is where you set your personal passphrase for end-to-end encryption (covered in Step 5).

Inside Settings → Cloud server in SMSGate you will see your Username and Password. These are your unique credentials that allow Calendo to authenticate with your phone.

Now, in Calendo:

1. Go to Admin → Business Settings → Notifications and scroll down to the SMSGate configuration section.
2. Tap Set SMSGate credentials.
3. Paste the Username and Password from the SMSGate app into the corresponding fields.
4. Save your settings.

SMSGate supports end-to-end encryption for the message content traveling between Calendo's servers and your phone. When enabled, the message text is encrypted before leaving Calendo and decrypted only on your device — SMSGate's cloud relay cannot read it.

To enable encryption:

1. In SMSGate, go to Settings → Encryption.
2. Enter a passphrase of your choice and save.
3. In Calendo, go to Admin → Business Settings → Notifications → SMSGate configuration and enter the same passphrase in the Encryption key field.

After completing the setup, check the status in Calendo's notification settings:

• SMSGate ready — Everything is working. Your clients will receive SMS reminders automatically.
• Device offline — The credentials are correct but your phone is not reachable. Open SMSGate on your phone and make sure Cloud server is enabled and the phone has an internet connection.
• No device registered — The credentials have not been entered yet, or there is a mismatch. Double-check the Username and Password.

Battery optimization

Android's battery optimization can kill background apps. To prevent SMSGate from being stopped, go to Settings → Battery → Battery optimization, find SMSGate in the list, and set it to Not optimized (or Unrestricted on some devices).

Dual SIM phones

If your phone has two SIM cards, you can choose which one SMSGate uses for sending messages. In SMSGate's Settings, look for the SIM card option and select the preferred SIM.

Credentials changed?

SMSGate generates your Username and Password automatically and they don't change unless you reinstall the app. If you reinstall SMSGate, generate fresh credentials and update them in Calendo.

Messages not being sent?

• Confirm the Cloud server toggle is on in SMSGate.
• Confirm the phone has an active internet connection.
• Check that the Username, Password, and Encryption key all match exactly in both apps.
• Make sure your mobile plan allows outgoing SMS messages.
• Check SMSGate's built-in Logs screen for error details.

Ready to send SMS reminders?

Log in to Calendo and go to Business Settings → Notifications to complete the SMSGate setup.