Sending Emails with Firebase Cloud Functions and SendGrid

How We Set Up https://us-central1-webstaremailsystem.cloudfunctions.net/sendOtpEmail for [company name]

When building apps that require sending verification emails, OTPs, or notifications, using a reliable and scalable cloud function is a game changer. In this guide, we’ll walk through the entire process of setting up a Firebase Cloud Function that sends email using SendGrid, including domain authentication to avoid the spam folder.

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🧱 Step 1: Set Up Firebase Project

1. Go to Firebase Console
   Visit https://console.firebase.google.com and create a new project (e.g., webstaremailsystem).

2. Enable Blaze Plan
   Firebase Cloud Functions that use external APIs (like SendGrid) require the Blaze (pay-as-you-go) plan.

   • Navigate to Settings > Usage and billing.

   • Click Modify plan and switch from Spark to Blaze.

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💻 Step 2: Install Firebase CLI and Initialize Functions

1. Install Firebase CLI

    npm install -g firebase-tools
   

2. Login to Firebase

    firebase login
   

3. Initialize Functions

    mkdir jetwave-functions
    cd jetwave-functions
    firebase init functions
   

   • Select: Use an existing project → choose webstaremailsystem

   • Language: JavaScript

   • Linting: No

   • Install dependencies: Yes

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🔐 Step 3: Set Up SendGrid

1. Sign Up at https://app.sendgrid.com

2. Generate API Key

   • Go to Settings > API Keys > Create API Key

   • Label it something like webstar-firebase

   • Copy and save the API key securely

3. Authenticate Your Domain

   • Go to Sender Authentication → Domain Authentication

   • Select DNS provider (e.g., Namecheap or manual cPanel entry)

   • Add the CNAME and TXT records in your domain’s cPanel

   • Wait for SendGrid to verify (can take minutes to hours)

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📦 Step 4: Add SendGrid to Firebase Function

1. Navigate to your functions folder:

    cd functions
    npm install @sendgrid/mail
   

2. Edit functions/index.js:

const functions = require("firebase-functions");
const sgMail = require("@sendgrid/mail");

// Replace with your actual SendGrid API key
sgMail.setApiKey("YOUR_SENDGRID_API_KEY");

exports.sendOtpEmail = functions.https.onRequest(async (req, res) => {
  const { email, name, subject, body } = req.body;

  if (!email || !subject || !body) {
    return res.status(400).json({ status: "error", message: "Missing required fields" });
  }

  const msg = {
    to: email,
    from: "info@domain.com", // Must be verified on SendGrid
    subject,
    html: body,
  };

  try {
    await sgMail.send(msg);
    res.status(200).json({ status: "success", message: "Email sent" });
  } catch (error) {
    console.error("SendGrid Error:", error);
    res.status(500).json({ status: "error", message: "Failed to send email" });
  }
});

3. Replace "YOUR_SENDGRID_API_KEY" with your actual key. You can use Firebase environment variables to keep this secret.

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🚀 Step 5: Deploy Function to Firebase

1. Deploy only functions:

    firebase deploy --only functions
   

2. Get your function URL:
   Firebase will return a URL like:
   https://us-central1-webstaremailsystem.cloudfunctions.net/sendOtpEmail

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📬 Step 6: Test Email Function

Send a POST request to the endpoint with a body like:

{
  "email": "recipient@example.com",
  "name": "User",
  "subject": "Your Webstar OTP",
  "body": "<p>Hello <strong>User</strong>, your OTP is <strong>9021</strong></p>"
}

You can test using tools like:

• Postman

• cURL

• JavaScript fetch() or axios in your frontend

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📝 Bonus Tips for Deliverability

• ✅ Make sure you verify your sending domain on SendGrid

• 📥 Ask your users to whitelist your sender email (info@domain.com)

• 💌 Add a valid DMARC record to improve sender trust

• 🕒 Emails might land in spam on first test — once verified, they should hit inbox

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✅ Conclusion

You now have a production-ready cloud function that sends emails using Firebase and SendGrid. This setup is scalable, serverless, and reliable — perfect for OTPs, password resets, and transactional emails in modern web/mobile apps.

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