Email API for Developers
Send transactional and campaign emails through a clean REST API or SMTP relay. Automatic DKIM/SPF, real-time webhooks, and a dashboard that doesn't get in your way.
Send an email in one request
curl -X POST https://api.relaypost.dev/v1/emails/send \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"from": "[email protected]",
"to": "[email protected]",
"subject": "Welcome to YourApp",
"html": "<p>Thanks for signing up.</p>"
}'No SDK required. Works with fetch(), curl, or any HTTP client in any language.
Built for developers, designed for scale
REST API + SMTP
Send via our JSON REST API or connect over SMTP (ports 587/465). Both support full authentication and delivery tracking.
Automatic authentication
DKIM signing and SPF alignment are configured automatically when you verify your domain. No manual DNS debugging.
Real-time webhooks
Get HTTP callbacks for delivery, bounce, complaint, open, and click events as they happen.
Transactional + campaigns
One platform for password resets and newsletters. No need to manage two email providers.
Suppression management
Bounces and complaints are automatically suppressed. Your sender reputation stays clean without manual work.
Transparent pricing
Start free with 1,000 emails/mo. Pro plan is $25/mo for 100K emails. No hidden fees or per-feature charges.
Works with any language
RelayPost uses a standard REST API. No proprietary SDK required — send emails with the HTTP client you already use.
Node.js
await fetch("https://api.relaypost.dev/v1/emails/send", {
method: "POST",
headers: {
"Authorization": "Bearer YOUR_API_KEY",
"Content-Type": "application/json"
},
body: JSON.stringify({
from: "[email protected]",
to: "[email protected]",
subject: "Hello",
html: "<p>It works.</p>"
})
});Python
import requests
requests.post(
"https://api.relaypost.dev/v1/emails/send",
headers={"Authorization": "Bearer YOUR_API_KEY"},
json={
"from": "[email protected]",
"to": "[email protected]",
"subject": "Hello",
"html": "<p>It works.</p>"
}
)Frequently asked questions
What is an email API?
An email API is a programmatic interface that lets your application send, receive, and track emails. Instead of configuring your own mail server, you send HTTP requests to the API and it handles delivery, authentication, bounce processing, and tracking.
What is the difference between transactional and marketing email?
Transactional emails are triggered by user actions — password resets, order confirmations, account notifications. Marketing emails are sent in bulk to a list — newsletters, promotions, product updates. RelayPost handles both through one API.
Do I need an email API or SMTP?
Both work for sending email. A REST API is easier to integrate with modern web frameworks and gives you programmatic control over tracking and templates. SMTP works with any language or tool that supports it. RelayPost supports both — use whichever fits your stack.
How fast can I integrate RelayPost?
Most developers send their first email within 5 minutes. Add your domain, verify DNS records, and make a single POST request. No SDK required — the API works with fetch() in any language.