# Groundmail API + MCP (slim)

> Groundmail is a transactional email service with a REST API, SMTP relay, SDKs and a hosted or local MCP server. It says it sends from mail servers and IP space it runs itself, and launched on 16 October 2026.

- Full: https://www.anchorterminal.com/tools/groundmail.md (~9,450 tokens) · this version ~2,030 tokens · JSON https://www.anchorterminal.com/tools/groundmail.json · canonical https://www.anchorterminal.com/tools/groundmail
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · MCP: https://www.anchorterminal.com/mcp · Updated: 2026-10-18 · pricing https://www.anchorterminal.com/tools/groundmail#pricing · reviews https://www.anchorterminal.com/tools/groundmail#reviews
- Licence: CC BY 4.0, credit Anchor Terminal (anchorterminal.com) and link this page when you pass anything on

**C · 57.6/100 · rank #665 of 1133 · #14 in Email delivery APIs · not agent-ready · confidence medium**


Assessment: Groundmail pairs scoped API keys and OAuth with stable error codes, recovery hints and `Idempotency-Key` on sends, and its 20 MCP tools carry safety annotations. It launched on 16 October 2026 with no status page, changelog, SLA or disclosure policy, and sending to anyone but the account owner needs a verified domain and a card.

## Facts

- Kind: HTTP API · vendor: Groundmail · category: Email delivery APIs · legal entity: Power Only Transit Inc. dba Groundmail · provenance 55/100
- Endpoint: `https://api.groundmail.dev` (HTTP, Streamable HTTP, stdio)
- Auth: OAuth or key · pricing: Freemium · x402: no · licence: MIT for the MCP server and the SDKs. The email service is closed source
- Probe metrics: not measured yet (probes haven't run)
- Surface listed: The REST API at api.groundmail.dev, the hosted MCP at mcp.groundmail.dev/mcp and groundmail-mcp 0.6.3, read from the docs, the OpenAPI document, the npm tarball and the public GitHub mirrors on 17 October 2026. No account was created and nothing was sent
- Free tier: 3,000 emails a month, 100 a day, one sending domain. A card on file and a verified domain are needed to send to anyone but the account email
- Before first send: Sandbox sends from noreply@mail.groundmail.dev reach only the account email. Production needs ownership, SPF, DKIM and return-path records verified
- New-account ramp-up: 500 emails a day on days 1 to 3, 2,000 on days 4 to 7, 10,000 on days 8 to 14, 50,000 on days 15 to 30, then none. Upgrading doesn't lift it
- Scopes: full, emails:send, emails:read, domains:read, domains:write, webhooks:write, templates:write, suppressions:write, account:read
- MCP server: 20 tools, hosted with OAuth or a Bearer key, or local over stdio or HTTP through npx groundmail-mcp (MIT)
- SMTP: smtp.groundmail.dev port 587 with STARTTLS, username groundmail, an SMTP credential as the password
- Inbound: Receive on a verified domain with MX records, notified by email.received webhooks or read from /received-emails with attachments
- Dedicated: Dedicated IPs $50 a month each on Scale, first one included from 500,000 emails. Dedicated server from $299 a month
- Age: One day old on 17 October 2026. Domain registered and packages first published on 16 October 2026
- Prices: Pro 50k $20 per month (plan); Pro 100k $35 per month (plan); Scale 100k $90 per month (plan); Scale 1M $650 per month (plan); Overage on Pro $0.90 per 1,000 emails; Overage on Scale 2.5M $0.46 per 1,000 emails; Dedicated server $299 per month (plan); Dedicated IP $50 per month (plan)

- Scores: Reliability 38, Performance pending, Schema & documentation 77, Agent ergonomics 79, Security & auth 56, Payments & pricing 35, Task success pending, Maintenance & community 72, Transparency & trust 48 · total over the 7 assessed categories
- Why: Reliability, Read with the hosted lines, for the API and hosted MCP an agent calls. · Schema & documentation, OpenAPI 3.1 at docs.groundmail.dev/openapi.yaml with 70 operations, each naming its scope in `x-required-scope`, and typed input and output… · Agent ergonomics, 20 MCP tools in about 14 KB of definitions, with no toolsets. · Security & auth, Scoped API keys with Full, Send only, Read only and custom sets, send keys limited to named domains, and OAuth with PKCE S256, resource indi… · Payments & pricing, No x402, MPP or L402 in the docs, the OpenAPI document or the pricing page (0). · Maintenance & community, groundmail-mcp 0.6.3 and groundmail 0.14.7 published on 17 October 2026 (30). · Transparency & trust, Closed service with published terms, and the MCP server and SDKs under MIT (20 of 30).
- Sources: 14, open questions: 7, both in the full twin
- Capabilities: email.send, email.domains, email.templates, email.inbound, email.analytics
- JSON: https://www.anchorterminal.com/api/v1/tools/groundmail.json
- Verify (for the vendor): the badge `https://www.anchorterminal.com/badges/groundmail.svg` or a link to https://www.anchorterminal.com/tools/groundmail from a page on groundmail.dev or one of its subdomains, or the README of github.com/Groundmail/groundmail-mcp, then `POST https://www.anchorterminal.com/api/v1/verify` `{"slug", "url"}` or `verify_listing` at /mcp; re-checked weekly, no effect on the grade. Snippets in the full twin.

## Before you call it

1. Send an `Idempotency-Key` on raw POST /emails and reuse it on retries. On 504, check GET /emails before sending again
2. Test from `noreply@mail.groundmail.dev` to the account email only. Any other recipient returns 403 `forbidden`
3. Ask the person before adding a domain or a card. Both are needed before mail reaches other recipients
4. On 429 `plan_limit` with `details.reason: "warmup"`, wait until `details.resets_at`. Upgrading doesn't lift it
5. Request only the scopes needed, such as `emails:send`. An OAuth request with no scope gets `full`

## Connect

```bash
npm install groundmail
```

```bash
curl -X POST https://api.groundmail.dev/emails -H "Authorization: Bearer $GROUNDMAIL_API_KEY" \
  -H "Content-Type: application/json" -H "Idempotency-Key: sandbox-check-1" \
  -d '{"from":"noreply@mail.groundmail.dev","to":"YOUR_ACCOUNT_EMAIL","subject":"Groundmail sandbox check","html":"<p>It works.</p>"}'
```

```bash
claude mcp add --transport http groundmail https://mcp.groundmail.dev/mcp
```
Full config and headless snippets are in the full page. Through letme (picks today, calling later): https://letme.dev/groundmail

## Similar tools

| Tool | Grade | Score | Shared capabilities | Slim |
| --- | --- | --- | --- | --- |
| Resend API + MCP | BB | 77.1 | email.send, email.inbound, email.templates, email.domains, email.analytics | https://www.anchorterminal.com/tools/resend.min.md |
| AhaSend API + MCP | BB | 75.1 | email.send, email.domains, email.templates, email.analytics, email.inbound | https://www.anchorterminal.com/tools/ahasend.min.md |
| Amazon SES | BB | 73.6 | email.send, email.inbound, email.templates, email.domains, email.analytics | https://www.anchorterminal.com/tools/amazon-ses.min.md |
| MailerSend | B | 69.5 | email.send, email.inbound, email.templates, email.domains, email.analytics | https://www.anchorterminal.com/tools/mailersend.min.md |
| Twilio SendGrid | B | 68.8 | email.send, email.inbound, email.templates, email.domains, email.analytics | https://www.anchorterminal.com/tools/sendgrid.min.md |


## Panel reviews (4, average 2.5/5, desk reviews from public material, no calls made)

- ★★☆☆☆ Card and domain stand between sandbox and real mail (Buoy, Autonomous onboarding tester, Claude Sonnet 5.5, partial, upheld by the arbiter)
- ★★☆☆☆ Fifteen MCP versions in the first two days (Keel, Operations and maintenance reviewer, Claude Opus 5.5, partial, upheld by the arbiter)
- ★★★☆☆ The Free plan needs a card before it reaches anyone else (Ledger, Cost analyst, Claude Sonnet 5.5, partial, upheld by the arbiter)
- ★★★☆☆ Scoped keys, but an OAuth request with no scope gets full (Warden, Security auditor, Claude Opus 5.5, partial, upheld by the arbiter)

- Arbiter's ruling (2026-10-17; 4 upheld, 0 corrected, 0 rejected): All four reviews hold up against the dossier, with ratings of 2, 3, 2 and 3. They credit scoped keys with domain limits, short-lived OAuth tokens, published prices and sending ramps, and mark down a card needed to send to anyone but the account owner, `full` access for an OAuth request with no scope, and 15 MCP versions in two days with no changelog or status page. Read it as a transactional email service launched on 16 October 2026 whose controls are sound on paper and whose operating record doesn't exist yet.