# Groundmail Transactional email API on mail servers and IPs Groundmail owns and runs. Send with HTTP, an official SDK (Node, Python, Go, PHP, Ruby), SMTP or MCP. ## Defaults 1. Base URL `https://api.groundmail.dev`, auth `Authorization: Bearer gm_…`, key in env `GROUNDMAIL_API_KEY` (server-side only). 2. Contract: https://docs.groundmail.dev/openapi.yaml · Index: https://docs.groundmail.dev/llms.txt · Full docs: https://docs.groundmail.dev/llms-full.txt 3. Test on the user's own address first (sandbox below). Ask before emailing anyone else, adding a domain or touching billing. 4. Send every email with an `Idempotency-Key` and reuse it on retries. 5. On errors, branch on `error.code` and follow `error.hint`. Related skills: `groundmail-mcp`, `groundmail-cli`, `email-best-practices`. --- ## Send: Node.js ```ts import { Groundmail, GroundmailError } from 'groundmail' const groundmail = new Groundmail(process.env.GROUNDMAIL_API_KEY!) try { const result = await groundmail.emails.send({ from: 'hello@yourdomain.com', to: 'user@example.com', subject: 'Welcome', html: '

It works.

', idempotencyKey: `welcome-${user.id}`, }) console.log(result.id, result.status) } catch (error) { if (error instanceof GroundmailError) { console.error(error.status, error.code, error.message) } throw error } ``` Install: `npm install groundmail`. The SDK **throws** `GroundmailError` (`status`, `code`, `message`, `details`); it does not return `{ data, error }`. ## Send: Go ```bash go get github.com/Groundmail/groundmail-sdks/go ``` ```go client, err := groundmail.New(os.Getenv("GROUNDMAIL_API_KEY")) result, err := client.Emails.Send(map[string]any{ "from": "hello@yourdomain.com", "to": "user@example.com", "subject": "Welcome", "html": "

It works.

", }) ``` Import path: `groundmail "github.com/Groundmail/groundmail-sdks/go"`. ## Send: Python, PHP, Ruby ```bash pip install groundmail # Python (Django backend: pip install 'groundmail[django]') composer require groundmail/groundmail # PHP composer require groundmail/laravel # Laravel (MAIL_MAILER=groundmail) composer require groundmail/symfony-mailer # Symfony Mailer transport gem install groundmail # Ruby (Rails: bundle add groundmail) ``` ```python tx = Groundmail(os.environ["GROUNDMAIL_API_KEY"]) # from groundmail import Groundmail tx.emails.send(from_="hello@yourdomain.com", to="user@example.com", subject="Welcome", html="

It works.

") ``` ```php $tx = new \Groundmail\Client(getenv('GROUNDMAIL_API_KEY')); $tx->emails->send(['from' => 'hello@yourdomain.com', 'to' => 'user@example.com', 'subject' => 'Welcome', 'html' => '

It works.

']); ``` ```ruby tx = Groundmail::Client.new(ENV.fetch("GROUNDMAIL_API_KEY")) # require "groundmail" tx.emails.send(from: "hello@yourdomain.com", to: "user@example.com", subject: "Welcome", html: "

It works.

") ``` Docs: https://docs.groundmail.dev/sdks/python · https://docs.groundmail.dev/sdks/php · https://docs.groundmail.dev/sdks/ruby · https://docs.groundmail.dev/frameworks/laravel · https://docs.groundmail.dev/frameworks/symfony. Any other language: use HTTP or SMTP. ## Send: HTTP ```bash curl -X POST https://api.groundmail.dev/emails \ -H "Authorization: Bearer $GROUNDMAIL_API_KEY" \ -H "Content-Type: application/json" \ -H "Idempotency-Key: welcome-8812" \ -d '{"from":"hello@yourdomain.com","to":"user@example.com","subject":"Welcome","html":"

It works.

"}' ``` Success: `{ "id": "msg_…", "status": "sent" }` (`"scheduled"` with `scheduled_at`). Canonical fields: `from`, `to`, `cc`, `bcc`, `reply_to`, `subject`, `html`, `text`, `scheduled_at`, `attachments`, `tags`, `headers`, `template`. Migration aliases (`htmlBody`, `replyTo`, …) are accepted, but generate canonical snake_case. ## Send: SMTP Host `smtp.groundmail.dev`, port `587` (STARTTLS), username `groundmail`, password an SMTP credential (`gmsmtp_…`) from the dashboard or `POST /smtp-credentials`. Same sandbox, domain and billing rules as the API. --- ## Test sends (safe by default) | Stage | `from` | `to` | Needs | |-------|--------|------|-------| | Sandbox | `noreply@mail.groundmail.dev` | The Groundmail account email only | Nothing | | Own domain, to self | Address on a verified domain | The account email only | Verified domain | | Production | Address on a verified domain | Anyone | Verified domain + payment method on file | Anything outside these rules returns `403` `forbidden` with a `hint`, and nothing is sent. Test sends are real deliveries to the account owner and count toward quota. `POST /emails/test` with `{"event":"email.bounced"}` delivers a simulated webhook event without sending email. Plans: Free ($0, 3,000/month, 100/day, 1 domain, never charged, card required to send to others) · Pro (from $20/month) · Scale (from $90/month) · Dedicated (from $299/month, your own servers and IPs). Do not recommend a plan change without the user asking. Docs: https://docs.groundmail.dev/ai/safe-defaults --- ## Idempotency - Header `Idempotency-Key` on `POST /emails` and `POST /events` (SDK: `idempotencyKey`), up to 256 characters, kept 24 hours per team. - Same key + same body: the original response is replayed, nothing is sent again. - Same key + different body, or first request still running: `409 idempotency_conflict`. - Use one key per logical message (`password-reset--`), store it with the job, reuse it on every retry. --- ## Errors ```json { "error": { "code": "forbidden", "message": "Sandbox sends are limited to owner@example.com. …", "hint": "Sandbox sends from noreply@mail.groundmail.dev only go to your own account email. …", "docs_url": "https://docs.groundmail.dev/errors#forbidden" } } ``` A few older endpoints return `error` as a string with `code`, `message`, `hint` and `docs_url` beside it: read `typeof body.error === 'object' ? body.error : body`. | Code | Status | Do this | |------|--------|---------| | `validation_error` | 400 / 422 | Fix the field in `message`/`details`. 422 = suppressed or opted-out recipients: do not resend to them | | `unauthorized` | 401 | Fix the `Authorization: Bearer gm_…` header | | `forbidden` | 403 | Follow `hint`: verify the domain, keep sandbox sends to the account email, or ask the user to add a payment method | | `insufficient_scope` | 403 | Use a key with the right scope | | `not_found` | 404 | List the collection to find the right id | | `conflict` | 409 | Reuse the existing resource | | `idempotency_conflict` | 409 | New key for a new message; wait and retry for in-progress | | `plan_limit` / `domain_limit` | 429 / 403 | Stop and tell the user (`upgrade_url`) | | `rate_limited` | 429 | Wait `Retry-After`, retry with the same key | | `upstream_error` | 502 / 503 | Retry with backoff and the same key | | `upstream_error` | 504 | May have been sent: check `GET /emails` before anything else | | `internal_error` / `not_configured` | 500 / 503 | Retry with backoff and the same key | Full list: https://docs.groundmail.dev/errors --- ## Domain verification 1. `POST /domains` with `{ "name": "yourdomain.com" }` 2. `POST /domains/{id}` with `{ "action": "apply", "provider": "cloudflare" }` (or `godaddy`, `vercel`), or publish the returned `records` by hand 3. `POST /domains/{id}` with `{ "action": "verify" }`. A `400` with `pending: true` means DNS has not propagated: retry in a minute or two, `checks` shows what is missing 4. Switch production `from` to an address on the verified domain Explain when the user still needs DNS or registrar access. --- ## Templates, webhooks, events - Send a published template: `template: { id: "", variables: { … } }` instead of `html`/`text`. Starters: `password-reset`, `email-verification`, `welcome`, `invoice`, `team-invite` (`POST /templates/from-starter`). - React Email: pass `react: ` with `@react-email/render` installed; the SDK renders it to HTML. Guide: https://docs.groundmail.dev/guides/react-email - Webhooks: `POST /webhooks`; events include delivered, bounced, complained. Verify signatures with the SDK helper. - `GET /emails`, `GET /emails/{id}` for status; `GET /deliverability` for best-effort metrics (not inbox placement guarantees). --- ## Anti-patterns - Putting `gm_` keys in browser, mobile or `NEXT_PUBLIC_`/`VITE_` variables (the API has no CORS on purpose) - Sending production mail from `noreply@mail.groundmail.dev` - Retrying sends without an `Idempotency-Key` - Parsing `message` instead of branching on `code` - Describing Groundmail as a clone of another provider in customer-facing copy ## MCP and CLI - MCP: hosted `https://mcp.groundmail.dev/mcp` (OAuth) or `npx -y groundmail-mcp`. See skill `groundmail-mcp` or https://docs.groundmail.dev/ai/mcp - CLI: skill `groundmail-cli`, `npx -y --package=groundmail-cli -- groundmail …`

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