Send Transactional Emails with Supabase Edge Functions Using Keplars

Supabase has become one of the most popular backend platforms for modern applications. With PostgreSQL, Authentication, Storage, Realtime, and Edge Functions built in, developers can build and scale products faster than ever.

But when it comes to sending transactional emails such as welcome emails, password resets, verification codes, notifications, and newsletters, developers still need a reliable email infrastructure.

That's where Keplars comes in.

With the Keplars Supabase Integration, you can deploy a production-ready Edge Function and start sending emails directly from your Supabase project in just a few minutes.

Why Use Keplars with Supabase?

The integration is built specifically for Supabase Edge Functions and provides:

• Template-based emails
• HTML and plain-text emails
• Scheduled email delivery
• Instant email delivery (0-5 seconds)
• Deno + TypeScript support
• Optional JWT authentication
• Production-ready deployment

Whether you're building a SaaS platform, marketplace, mobile application, AI product, or internal tool, Keplars makes email delivery simple and scalable.

Getting Started

1. Clone the Example Repository

Start by cloning the official example:

1git clone https://github.com/KeplarsHQ/supabase-example.git
2
3cd supabase-example

2. Configure Your API Key

Navigate to the Supabase folder:

1cd supabase
2
3cp .env.local.example .env.local

Add your Keplars API key:

1KEPLARS_API_KEY=kms_your_actual_api_key_here

3. Start Supabase Locally

Launch your local Supabase environment:

1supabase start

Your Edge Function will be available at:

1http://127.0.0.1:54321/functions/v1/keplars-email-function

Send Your First Email

Once the function is running, sending emails is as simple as making an HTTP request.

Template-Based Email

1{
2  "to": ["[email protected]"],
3  "template_id": "your_template_id",
4  "params": {
5    "user_name": "John Doe",
6    "verification_code": "123456"
7  },
8  "delivery_type": "instant"
9}

Perfect for:

• Welcome emails
• Email verification
• OTP delivery
• Password reset emails
• Transactional notifications

Plain Text Emails

Need something simple?

1{
2  "to": ["[email protected]"],
3  "subject": "Welcome!",
4  "body": "Thanks for signing up. We're excited to have you.",
5  "delivery_type": "instant"
6}

HTML Emails

For complete control over your email design:

1{
2  "to": ["[email protected]"],
3  "subject": "Welcome!",
4  "html": "<h1>Welcome!</h1><p>Thanks for signing up.</p>",
5  "is_html": true,
6  "delivery_type": "instant"
7}

HTML emails are ideal for:

• Product announcements
• Marketing campaigns
• Customer onboarding
• Event invitations

Scheduled Emails

Keplars also supports scheduled delivery with timezone support.

1{
2  "to": ["[email protected]"],
3  "subject": "Weekly Newsletter",
4  "html": "<h1>This Week's Updates</h1>",
5  "scheduled_at": "2026-01-25T10:00:00",
6  "timezone": "America/New_York"
7}

Use scheduled delivery for:

• Weekly newsletters
• Subscription reminders
• Product launches
• Time-based workflows

Calling Keplars from Supabase

One of the biggest advantages of this integration is how naturally it fits into existing Supabase applications.

JavaScript / TypeScript Example

1import { createClient } from '@supabase/supabase-js'
2
3const supabase = createClient(
4  'https://your-project-ref.supabase.co',
5  'your-anon-key'
6)
7
8const { data, error } =
9  await supabase.functions.invoke(
10    'keplars-email-function',
11    {
12      body: {
13        to: ['[email protected]'],
14        template_id: 'your_template_id',
15        params: {
16          user_name: 'John',
17          verification_code: '123456'
18        },
19        delivery_type: 'instant'
20      }
21    }
22  )
23
24if (error) {
25  console.error(error)
26} else {
27  console.log(data)
28}

This makes email delivery feel like a native part of the Supabase ecosystem.

React Example

If you're building a React application, you can trigger emails like this:

1import { useSupabaseClient }
2from '@supabase/auth-helpers-react'
3
4function WelcomeEmail() {
5  const supabase = useSupabaseClient()
6
7  const sendWelcome = async (
8    email: string,
9    name: string
10  ) => {
11    await supabase.functions.invoke(
12      'keplars-email-function',
13      {
14        body: {
15          to: [email],
16          template_id:
17            'your_welcome_template_id',
18          params: {
19            user_name: name
20          }
21        }
22      }
23    )
24  }
25
26  return (
27    <button
28      onClick={() =>
29        sendWelcome(
30          '[email protected]',
31          'Jane'
32        )
33      }
34    >
35      Send Welcome Email
36    </button>
37  )
38}

Next.js Integration

Using Supabase with Next.js? You can trigger emails directly from API routes.

1import { createClient }
2from '@supabase/supabase-js'
3
4export async function POST(
5  request: Request
6) {
7  const { email, name } =
8    await request.json()
9
10  const supabase = createClient(
11    process.env.NEXT_PUBLIC_SUPABASE_URL!,
12    process.env.SUPABASE_SERVICE_ROLE_KEY!
13  )
14
15  const { data, error } =
16    await supabase.functions.invoke(
17      'keplars-email-function',
18      {
19        body: {
20          to: [email],
21          template_id:
22            process.env.KEPLARS_TEMPLATE_ID,
23          params: {
24            user_name: name
25          }
26        }
27      }
28    )
29
30  return Response.json({
31    success: !error,
32    data
33  })
34}

Deploying to Production

Once you're ready to go live, follow these steps.

Link Your Project

1supabase link --project-ref your-project-ref

Store Secrets Securely

1supabase secrets set \
2KEPLARS_API_KEY=kms_your_actual_api_key_here

Deploy the Function

1supabase functions deploy \
2keplars-email-function

Your endpoint will be available at:

1https://your-project-ref.supabase.co/functions/v1/keplars-email-function

Production Security

For production deployments, we strongly recommend enabling JWT verification.

Update your `supabase/config.toml`:

1[functions.keplars-email-function]
2verify_jwt = true

This ensures only authenticated users can invoke your email endpoint.

Email Delivery Response

Successful requests return the following delivery metadata.

1{
2  "id": "msg_...",
3  "object": "email",
4  "status": "queued",
5  "from": "[email protected]",
6  "to": ["[email protected]"],
7  "created_at": "2026-01-22T22:14:04.470Z"
8}

This makes it easy to track and monitor email activity across your application.

Why Developers Choose This Integration

Developers already use Supabase to simplify backend infrastructure. Keplars does the same for email infrastructure.

Instead of managing SMTP servers, provider integrations, deliverability issues, retries, and email queues, you can deploy a single Edge Function and start sending production-ready emails immediately.

Final Thoughts

Supabase Edge Functions provide a powerful serverless environment for modern applications. Combined with Keplars, they become a complete communication layer capable of sending transactional, marketing, and scheduled emails at scale.

If you're already building with Supabase, integrating Keplars takes only a few minutes and gives your application access to reliable, developer-friendly email delivery from day one.

Useful Links:

• Supabase Integration Docs
• Keplars Platform
• Documentation