SuperSend TX — Quickstart

Send your first transactional email in about five minutes.

Migrating from another provider? Start with Resend, Postmark, Amazon SES, or SendGrid, then mirror send + webhook flows from the hosted API Explorer.

Building auth email? See password reset, Supabase Auth, and Clerk / Auth.js.

Using React Email components? See Send React Email.

Hosted docs: docs.supersendtx.com
Dashboard: app.supersendtx.com
API: https://api.supersendtx.com

For AI agents

• Index: docs.supersendtx.com/llms.txt
• Full bundle: docs.supersendtx.com/llms-full.txt
• OpenAPI: docs.supersendtx.com/openapi.yaml
• Agent skill notes: docs.supersendtx.com/ai/agent-skill
• MCP server: docs.supersendtx.com/ai/mcp (supersendtx-mcp on npm)
• AI app builders: docs.supersendtx.com/builders (Lovable, Replit, Bolt, Base44, v0 prompts)

Use the dashboard Get started page to copy a personalized setup prompt with your API key and sandbox rules.

1. Create an account

1. Open the dashboard at app.supersendtx.com.
2. Sign up with email + password (or email code if you prefer).
3. If using email code: enter the code emailed to you.

2. Send a sandbox test (fastest path)

On Get started (/overview), choose one of two doors:

Set it up here (dashboard)

1. Click Send test email. We create an API key if needed and send to your account email (sandbox sender before DNS; your verified domain after).
2. Check your inbox for the test message.
3. Copy the stx_… secret if shown (once).

No domain or DNS required for the first sandbox send. After you verify a domain, the same button self-tests from that domain (still to your account email on Sandbox).

Use with Cursor or Claude

1. On Get started, click Copy setup prompt or Install in Cursor.
2. Paste the prompt into your editor, or add the supersendtx-mcp MCP server with your API key.
3. Let the agent wire POST /emails (or the SDK) into your app and run the sandbox self-test.

See docs/ai/agent-skill.md and docs/ai/mcp.md.

3. Create an API key (if you skipped the dashboard flow)

1. Go to API Keys → Create (or use an existing stx_… key).
2. Copy the secret — it is shown once.

export SUPERSENDTX_API_KEY=stx_your_key_here

4. Verify a sending domain (DNS setup — self-test from your domain on free)

Add and verify your domain on Sandbox to complete DNS setup. On the free plan you can self-test from your verified domain to your account email to confirm DNS and branding. Free production (send to other recipients) unlocks after a verified domain and a payment method on file — we do not charge until you upgrade. Caps: 3,000 emails/mo · 100/day · 1 domain. Upgrade to Pro or Scale for more volume.

Dashboard (recommended)

1. Go to Domains → Add domain and enter your domain (e.g. yourdomain.com).
2. On the domain page (or in guided setup):
   • If your DNS is on Cloudflare: click Sign in to Cloudflare when offered — authorize once and we add the records.
   • Or Settings → Integrations → paste a Cloudflare API token (Zone DNS Edit) → Save, then Apply DNS (Cloudflare).
   • If your DNS is at GoDaddy: switch to GoDaddy, paste an API key + secret for a one-time apply.
   • Otherwise paste the shown TXT records at your DNS host (merge SPF if you already have one).
3. Click Verify DNS.
4. Optional after verification: set Delivery settings on the domain detail page for:
   • open tracking
   • click tracking
   • tls_mode (opportunistic or enforced)
5. Check the built-in DMARC/BIMI guidance on the same page before you roll out branded inbox features.

Ownership, SPF, DKIM, and return-path are required to verify. Verify also confirms mail-server DKIM readiness so sends are signed with your domain (not the shared pool). Local Docker auto-verifies when SUPERSENDTX_DEV_AUTO_VERIFY=true. If a domain is already attached to another SuperSend TX team, POST /domains returns a 409 with claim instructions instead of creating a duplicate owner.

CLI (from your editor / terminal)

Save a Cloudflare token under Settings → Integrations first (recommended). Then:

export SUPERSENDTX_API_KEY=stx_your_key_here

npx -y --package=supersendtx-cli -- supersendtx domains add yourdomain.com

# Uses the Cloudflare token stored in SuperSend TX (no local CLOUDFLARE_API_TOKEN needed)
npx -y --package=supersendtx-cli -- supersendtx domains apply yourdomain.com --provider cloudflare

npx -y --package=supersendtx-cli -- supersendtx domains verify yourdomain.com

Optional override: set CLOUDFLARE_API_TOKEN locally to apply with a machine token instead of the dashboard one. Vercel uses VERCEL_API_TOKEN and optional VERCEL_TEAM_ID the same way. GoDaddy can use stored dashboard credentials or local GODADDY_API_KEY / GODADDY_API_SECRET.

5. Send from your app

Pick one integration method below. Replace [email protected] with an address on your verified domain.

Sandbox self-test (before DNS)

Use the shared sandbox sender on mail.supersendtx.com, but only send to your own account email:

curl -X POST https://api.supersendtx.com/emails \
  -H "Authorization: Bearer $SUPERSENDTX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "[email protected]",
    "to": "[email protected]",
    "subject": "Sandbox check",
    "html": "<p>SuperSend TX sandbox works.</p>"
  }'

Once your domain is verified, you can self-test from your own domain to your account email:

curl -X POST https://api.supersendtx.com/emails \
  -H "Authorization: Bearer $SUPERSENDTX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "[email protected]",
    "to": "[email protected]",
    "subject": "Verified domain check",
    "html": "<p>My domain works.</p>"
  }'

Add a payment method at Settings → Billing to unlock Free production (send to other recipients). Upgrade to Pro or Scale for more volume.

curl (production)

curl -X POST https://api.supersendtx.com/emails \
  -H "Authorization: Bearer $SUPERSENDTX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "[email protected]",
    "to": "[email protected]",
    "subject": "Hello from SuperSend TX",
    "html": "<p>It works.</p>"
  }'

Node.js SDK

npm install supersendtx

import { SuperSendTX } from 'supersendtx'

const client = new SuperSendTX(process.env.SUPERSENDTX_API_KEY!)

const { id, status } = await client.emails.send({
  from: '[email protected]',
  to: '[email protected]',
  subject: 'Hello from SuperSend TX',
  html: '<p>It works.</p>',
})

console.log(id, status)

CLI

SUPERSENDTX_API_KEY=$SUPERSENDTX_API_KEY npx -y --package=supersendtx-cli -- supersendtx emails send \
  --from [email protected] \
  --to [email protected] \
  --subject "Hello from SuperSend TX" \
  --html "<p>It works.</p>"

Or install globally: npm install -g supersendtx-cli, then run supersendtx emails send ….

Success response

{
  "id": "msg_abc123…",
  "status": "sent"
}

Plan limits

When billing is enabled, Sandbox is for integration and self-test sends (hard daily and monthly caps). Until Free production is unlocked, sends are limited to your account email — from the shared sandbox sender or from a verified domain. Unlock Free production with a verified domain and a payment method on file (no charge until you upgrade). Paid Pool and Dedicated plans meter overage past included volume. Over Free/Sandbox limit:

{ "error": { "message": "…", "code": "plan_limit", "upgrade_url": "/settings/billing" } }

HTTP 429. Upgrade in the dashboard under Settings → Billing.

Common errors

Full reference: docs.supersendtx.com/api-reference

6. Webhooks (optional)

1. Go to Webhooks in the dashboard (or use the API).
2. Add your HTTPS endpoint URL.
3. Copy the signing secret (whsec_…) — shown once.
4. Verify SuperSendTX-Signature on incoming POSTs.

await client.webhooks.create({
  url: 'https://yourapp.com/webhooks/supersendtx',
})

See docs.supersendtx.com/api-reference for payload shape and signature verification.

7. Receive email (optional)

Want an app inbox or agent mailbox?

1. Create a dedicated inbound subdomain such as inbound.example.com.
2. Add it with inbound_enabled: true (API) or supersendtx domains add inbound.example.com --inbound true (CLI).
3. Verify the domain, then publish the returned MX record.
4. Subscribe to email.received and/or poll GET /received-emails.

See docs/api/inbound.md for the full flow and the MX conflict warning.

8. Event-driven automations (optional)

SuperSend TX can trigger transactional sequences from custom events.

Dashboard: open Automations, create from a starter (or blank) on the visual canvas, configure steps in the side panel (send-email can use a published Templates entry or inline HTML), then Activate.

CLI / API: create and activate from a JSON file (handy in Cursor or CI):

supersendtx automations create --file ./welcome.json
supersendtx automations activate --id "$AUTOMATION_ID"

Then send the trigger event from your app:

curl -X POST https://api.supersendtx.com/events \
  -H "Authorization: Bearer $SUPERSENDTX_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: evt_user_created_123" \
  -d '{
    "name": "user.created",
    "user_id": "user_123",
    "email": "[email protected]",
    "data": {
      "name": "Ada Lovelace"
    }
  }'

Response:

{
  "event": {
    "id": "ae_123",
    "name": "user.created",
    "user_id": "user_123",
    "email": "[email protected]",
    "data": { "name": "Ada Lovelace" },
    "source": "api",
    "created_at": "2026-07-26T12:00:00.000Z"
  },
  "matched_automations": 1,
  "resumed_runs": 0,
  "cancelled_runs": 0
}

See docs/api/automations.md and docs/api/events.md.

Next steps

• Docs home: docs.supersendtx.com
• API reference: docs.supersendtx.com/api-reference
• Next.js quickstart: docs.supersendtx.com/frameworks/nextjs
• React Email: docs.supersendtx.com/guides/react-email
• Node.js quickstart: docs.supersendtx.com/frameworks/node
• Send API: docs/api/emails.md
• Domains API: docs/api/domains.md
• Inbound email API: docs/api/inbound.md
• Deliverability: docs/api/deliverability.md
• Events: docs/api/events.md
• Templates: docs/api/templates.md
• Automations: docs/api/automations.md
• SMTP relay: docs/api/smtp.md
• Webhooks: docs/api/webhooks.md
• AI onboarding: docs.supersendtx.com/llms.txt, docs.supersendtx.com/llms-full.txt, docs/ai/agent-skill.md, docs/ai/mcp.md (supersendtx-mcp npm package)
• OpenAPI spec: docs.supersendtx.com/openapi.yaml