Overview

High-performance email API with a Redis-based priority queue. Send transactional and marketing email at any scale.

Keplars is a developer-first email API built around a 4-tier priority queue. Route critical messages like OTP codes through /instant (0-5 sec delivery) and bulk campaigns through /bulk (idle processing) - all from the same API key.

New: Build with AI

Install the Keplars skill to let AI agents write your integration code correctly on the first try.

npx skills add KeplarsHQ/keplars-skills

Key Features

Priority Queue

4-tier Redis queue: instant (0-5s), high (0-30s), normal (0-5min), bulk (idle). Route each email to the right tier.

Multi-Provider

Gmail OAuth, Microsoft 365, SMTP, and AWS SES. Automatic failover and token refresh built in.

Dual Auth

Session-based OAuth for the dashboard, Bearer API keys for programmatic access. Same workspace, both methods.

AI Templates

Generate production-ready email templates from a plain-text prompt. Built-in content guardrails included.

Webhooks

Real-time delivery events: queued, sent, delivered, opened, clicked, bounced. HMAC-SHA256 signed.

Analytics

Live queue stats, delivery rates, bounce tracking, and open/click metrics in the dashboard.

Quick Start

Create your account

Connect an email provider

Link Gmail OAuth, Microsoft 365, or configure your own SMTP credentials in workspace settings.

Email Connection guide →

Generate an API key

Go to Settings → API Keys in your workspace and create a key. Store it as KEPLARS_API_KEY.

API Keys guide →

Send your first email

curl -X POST https://api.keplars.com/api/v1/send-email/async \
  -H "Authorization: Bearer $KEPLARS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "to": ["[email protected]"],
    "subject": "Hello from Keplars",
    "body": "<h1>It works!</h1>"
  }'

await fetch("https://api.keplars.com/api/v1/send-email/async", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KEPLARS_API_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    to: ["[email protected]"],
    subject: "Hello from Keplars",
    body: "<h1>It works!</h1>",
  }),
});

import requests, os

requests.post(
    "https://api.keplars.com/api/v1/send-email/async",
    headers={"Authorization": f"Bearer {os.getenv('KEPLARS_API_KEY')}"},
    json={
        "to": ["[email protected]"],
        "subject": "Hello from Keplars",
        "body": "<h1>It works!</h1>",
    },
)

Priority Queue Reference

Endpoint	Use Case	Delivery
`POST /send-email/instant`	OTP, 2FA, password reset	0-5 sec
`POST /send-email/high`	Security alerts, account notifications	0-30 sec
`POST /send-email/async`	Welcome emails, receipts, confirmations	0-5 min
`POST /send-email/bulk`	Newsletters, marketing campaigns	Idle
`POST /send-email/schedule`	Future-dated delivery	Scheduled

Default to /async. Only escalate when real-time delivery genuinely matters.