Product
Email API for transactional mail
A send email API for messages that have to arrive — receipts, auth mail, alerts — over HTTP, official SDKs, SMTP, the CLI, or MCP on infrastructure we operate.
- Free production after domain + card
- HTTP · SDKs · SMTP · CLI · MCP
- Node · Python · PHP · Ruby · Go
- Free → Dedicated, same API
Clarify
Send email API — not a mailbox sync API
Search results for “email API” mix two products. Pick the wrong one and you will fight OAuth scopes and inbox sync when you only needed to send from your domain.
Transactional send API (this page)
Your backend POSTs mail from a verified domain with an API key. You get delivery webhooks, suppressions, and a path to Pool or Dedicated. Built for product email — not reading a user’s inbox.
Emails API →Mailbox / sync APIs (different job)
Gmail API, Microsoft Graph, and inbox platforms authenticate as the user to read and send from their mailbox. Use those when the product is email client features — not branded transactional mail from noreply@yourdomain.
What is transactional email →SuperSend TX is a transactional email API: authenticate with a Bearer stx_ key, call POST /emails, and keep production traffic on a transactional network — not mixed with cold outbound or marketing blasts.
Protocol
HTTP email API vs SMTP relay
Most teams use both: HTTP for app code, SMTP where the vendor only offers SMTP credentials.
- HTTP: structured JSON, idempotency keys, batch up to 100, schedule send/update/cancel, signed webhooks
- SMTP: smtp.supersendtx.com:587 for Supabase, Clerk, WordPress, and legacy libraries — same domains and guardrails
- Prefer HTTP for new services so retries and observability stay in your app logs
- Prefer SMTP when Auth or a CMS only exposes SMTP host, port, and credentials
Deep dive on SMTP: SMTP relay. Auth wiring: Auth provider email.
Integrate
Pick the surface that fits your stack
Same account, domains, billing, and suppressions whether you call REST, install an SDK, relay SMTP, or wire an agent.
HTTP API
POST /emails from any language — curl, serverless, or your own client. Batch, schedule, and idempotency built in.
Emails API →Official SDKs
Node, Python, PHP, Ruby, and Go — plus a Laravel package. Types, retries, and helpers for webhooks and domains.
Node SDK →SMTP relay
smtp.supersendtx.com:587 for Supabase, Clerk, and legacy SMTP clients — same guardrails as HTTP.
SMTP →CLI
Scripts, local debugging, and CI with broad API parity — no dashboard required.
CLI + emails →MCP & agents
Hosted MCP with OAuth, local stdio, and Agent Skills for Cursor and similar agents.
MCP →Every install path
supersendtx (npm), supersendtx (PyPI), supersendtx/supersendtx (Composer), supersendtx/laravel (Laravel), supersendtx (RubyGems), github.com/Super-Send/supersendtx-sdks/go (Go).
Quickstart →Send
One endpoint to send email
No SDK required — call POST /emails with a Bearer stx_ key from any stack. That is the core send email API.
Batch
Up to 100
per request
Schedule
Native
send · update · cancel
Idempotency
Built in
safe retries
Attachments
Up to 10
per message
Example send
curl -X POST https://api.supersendtx.com/emails \
-H "Authorization: Bearer stx_…" \
-H "Content-Type: application/json" \
-d '{
"from": "[email protected]",
"to": "[email protected]",
"subject": "Welcome",
"html": "<p>You are in.</p>"
}'- · SDKs: Node, Python, PHP, Ruby, Go (+ Laravel)
- · CLI: npx -y --package=supersendtx-cli -- supersendtx emails send
- · SMTP: smtp.supersendtx.com:587
Node SDK
npm install supersendtx
import { SuperSendTX } from 'supersendtx'
const client = new SuperSendTX(process.env.SUPERSENDTX_API_KEY)
await client.emails.send({
from: '[email protected]',
to: '[email protected]',
subject: 'Welcome',
html: '<p>You are in.</p>',
})- · Python: pip install supersendtx
- · PHP: composer require supersendtx/supersendtx
- · Ruby: gem install supersendtx
- · Go: go get github.com/Super-Send/supersendtx-sdks/go
SDKs
Typed clients when you want them
Official SDKs wrap the same email API with helpers for domains, webhooks, templates, and suppressions.
- Same send path as HTTP and SMTP
- React Email via the Node SDK
- Webhook signature verification in every language
- Laravel config and facade for PHP teams
When not us
Choose a different email API when…
We would rather you pick the right category than force-fit SuperSend TX.
- You need Amazon SES DIY economics and already own AWS deliverability ops
- Campaigns, lists, and contact-based marketing are the product — use a marketing ESP
- You need to sync or read a user’s Gmail/Outlook mailbox — use a mailbox API
- Cold outbound or LinkedIn automation is the job — that is a different SuperSend product line
Platform
Beyond the first send
Inbound, webhooks, templates, and automations sit on the same platform when you need them.
Inbound email
Receive mail on your domain and drive reply workflows from webhooks or the API.
Templates
Visual editor with versioned publish. Teammates edit in the dashboard; engineers send by alias.
Automations
Turn product events into multi-step transactional email flows.
SMTP relay
Keep SMTP clients; get SuperSend TX domains, billing, and suppressions.
MCP & agents
Hosted MCP, OAuth, and Agent Skills so agents can send and operate safely.
- Signed webhooks for delivered, bounced, complained, opened, and clicked
- Visual block editor with versioned publish and a starter gallery
- Deliverability insights over 7 and 30 days
- Migrations from Resend, Postmark, SES, and SendGrid
Get started
From API key to production in four steps
Built for product email — receipts, auth mail, alerts — on a pipe that does not share fate with marketing blasts.
- 1
Create an account
Sign up free — self-test without a card.
- 2
Verify a domain
Add DNS records or one-click apply for Cloudflare and GoDaddy.
- 3
Unlock Free production
Add a payment method (no charge until you upgrade), then send to real recipients within Free caps.
- 4
Grow volume
Upgrade to Pro or Scale when you need more volume, or book Dedicated for isolation.
Infrastructure
Free to Dedicated without changing your code
We run the mail servers. We do not resell Amazon SES as the product.
Free
$0
3,000/mo · domain + card
Pro
From $20/mo
50k+ · 10 domains
Scale
Volume slider
up to 1,000 domains
Dedicated
From $299/mo
managed servers & IPs
Common jobs
What teams ship first
Same send path over HTTP, SDK, or SMTP — pick the integration that matches your auth stack.
- Password reset and verification emails
- Supabase Auth via Send Email hook or SMTP
- Clerk and Auth.js transactional mail
- Receipts, invoices, and product alerts
FAQ
Email API FAQ
What is an email API?
An email API lets your app send (and often track) mail over HTTP instead of running your own mail servers. For product mail — password resets, receipts, alerts — you typically POST JSON with from, to, subject, and html or text, authenticate with an API key, and receive delivery events via webhooks. That is different from mailbox APIs (Gmail, Microsoft Graph, Nylas) that read and sync a user’s inbox.
What is a send email API vs SMTP?
A send email API is an HTTP endpoint (for SuperSend TX, POST /emails with a Bearer stx_ key) with structured responses, idempotency, batching, and webhooks. SMTP is a protocol clients speak to a relay host — useful for Auth providers, WordPress plugins, and legacy libraries. Many teams use HTTP for new app code and SMTP where the integration only exposes SMTP credentials. SuperSend TX supports both on the same account and domains.
Is there a free email API?
Yes — Free on SuperSend TX includes production sending after you verify a domain and add a payment method (we do not charge until you upgrade). Caps are 3,000 emails/mo and 100/day on one domain. You can sign up and self-test without a card first. Pro starts at $20/mo when you need more volume. Treat “unlimited free email API” claims carefully: uncapped production sending is rare, and many free tiers share reputation with noisy neighbors.
Which languages work with this email API?
Any language that can make HTTPS requests can call POST /emails. Official SDKs cover Node, Python, PHP, Ruby, and Go, plus a Laravel package. There is also an SMTP relay, a CLI for scripts and CI, and hosted MCP for agents. Start from the quickstart if you want the shortest path in your stack.
When should I not use SuperSend TX?
Stay on Amazon SES if you already own AWS deliverability ops and want the lowest raw send cost. Prefer a marketing ESP (or a unified marketing+transactional vendor) if campaigns and contact databases are the product. Use Gmail or Microsoft Graph if you need to read a user’s mailbox, not send branded transactional mail from your domain. SuperSend TX is for transactional and relational product email on infrastructure we operate.
How is this different from a marketing email API?
Marketing APIs optimize lists, campaigns, and contact pricing. A transactional email API optimizes reliable, event-driven product messages. SuperSend TX keeps Pool traffic on a transactional network — not mixed with cold outbound or blast marketing — so a noisy campaign on another customer’s account is less likely to share fate with your password resets. Dedicated adds managed servers and IPs when isolation matters.
SuperSend TX is now Ranla
Same critical transactional email on the same infrastructure — signup and pricing live on ranla.ai, with an AI growth marketer included.