SuperSend TX — Quickstart

Send your first transactional email in about five minutes.

Migrating from Resend? Start with docs/migration.md for the minimal send-payload differences and sandbox guidance, then mirror your existing send + webhook flows from the hosted API reference.

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

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. Create an API key

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

3. Verify a sending domain (CLI or dashboard)

Dashboard (recommended)

1. Optional but easiest: Settings → Integrations → paste a Cloudflare API token (Zone DNS Edit) → Save.
2. Go to Domains → Add domain and enter your domain (e.g. yourdomain.com).
3. On the domain page:
   • If Cloudflare is connected: click Apply DNS (Cloudflare), then Verify DNS.
   • If your DNS is at GoDaddy: switch to GoDaddy, paste an API key + secret for a one-time apply, then Verify DNS.
   • Otherwise paste the shown TXT records at your DNS host (merge SPF if you already have one), then 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. 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. GoDaddy still uses local GODADDY_API_KEY / GODADDY_API_SECRET.

4. Send your first email

Pick one integration method below. Replace you@yourdomain.com with an address on your verified domain.

Need a quick self-test before DNS is ready? 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": "noreply@mail.supersendtx.com",
    "to": "you@example.com",
    "subject": "Sandbox check",
    "html": "<p>SuperSend TX sandbox works.</p>"
  }'

Once your domain is verified, switch from to your own domain.

curl (production)

curl -X POST https://api.supersendtx.com/emails \
  -H "Authorization: Bearer $SUPERSENDTX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "you@yourdomain.com",
    "to": "user@example.com",
    "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: 'you@yourdomain.com',
  to: 'user@example.com',
  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 you@yourdomain.com \
  --to user@example.com \
  --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, Free / Pro / Scale enforce hard monthly (and Free daily) caps. Over 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

5. 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.

6. 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.

7. 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": "user@example.com",
    "data": {
      "name": "Ada Lovelace"
    }
  }'

Response:

{
  "event": {
    "id": "ae_123",
    "name": "user.created",
    "user_id": "user_123",
    "email": "user@example.com",
    "data": { "name": "Ada Lovelace" },
    "source": "api",
    "created_at": "2026-07-26T12:00:00.000Z"
  },
  "matched_automations": 1,
  "resumed_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
• 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 status: docs/api/smtp.md
• Webhooks: docs/api/webhooks.md
• AI onboarding: docs.supersendtx.com/llms.txt, public/llms.txt, docs/ai/agent-skill.md, docs/ai/mcp.md
• OpenAPI spec: docs.supersendtx.com/openapi.yaml · openapi/supersendtx.yaml
• Product plan: PLAN.md