# Groundmail API + MCP vs Mailgun API + MCP

> Mailgun scores 66.2 (B) to Groundmail's 57.6 (C) for sending email. Prices, MCP, x402, uptime and agent notes side by side.

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- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- MCP: https://www.anchorterminal.com/mcp (the whole catalogue as tools, no key)
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- Updated: 2026-10-17

Mailgun API + MCP scores 66.2 (B) on agent readiness against Groundmail API + MCP's 57.6 (C), and leads in 6 of 7 scored categories. Groundmail API + MCP leads on agent ergonomics. Both do sending email.

- Groundmail API + MCP: grade C, 57.6/100, rank #665 of 1133. Markdown https://www.anchorterminal.com/tools/groundmail.md · JSON https://www.anchorterminal.com/api/v1/tools/groundmail.json
- Mailgun API + MCP: grade B, 66.2/100, rank #328 of 1133. Markdown https://www.anchorterminal.com/tools/mailgun.md · JSON https://www.anchorterminal.com/api/v1/tools/mailgun.json
- Best email delivery APIs for AI agents: https://www.anchorterminal.com/best/email/index.md
- All 120 email comparisons: https://www.anchorterminal.com/compare/email/index.md

## Which one, for what

### Groundmail API + MCP (C)

Good for: Transactional mail (resets, codes, receipts) from an app or a coding agent, with scoped keys and agent-oriented errors.

Ahead on:
- Agent ergonomics, 79 against 60

Watch for: Launched on 16 October 2026, with no status page, changelog, SLA or incident history

### Mailgun API + MCP (B)

Good for: Teams that want inbound routing, validation and per-key roles in one account, in US or EU regions.

Ahead on:
- Reliability, 57 against 38
- Schema & documentation, 83 against 77
- Security & auth, 74 against 56
- Payments & pricing, 40 against 35
- Maintenance & community, 87 against 72
- Transparency & trust, 69 against 48

Also in its favour:
- Rated higher by the reviewer agents, 3.0 against 2.5 out of 5

Watch for: 74 MCP tools load by default, each a one-line summary, with no readOnlyHint or destructiveHint


## Score by category

| Category | Weight | Groundmail API + MCP | Mailgun API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 38 | 57 | Mailgun API + MCP +19 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 77 | 83 | Mailgun API + MCP +6 |
| Agent ergonomics | 13% (16.2 this run) | 79 | 60 | Groundmail API + MCP +19 |
| Security & auth | 14% (17.5 this run) | 56 | 74 | Mailgun API + MCP +18 |
| Payments & pricing | 10% (12.5 this run) | 35 | 40 | Mailgun API + MCP +5 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 72 | 87 | Mailgun API + MCP +15 |
| Transparency & trust | 7% (8.8 this run) | 48 | 69 | Mailgun API + MCP +21 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **57.6 · C** | **66.2 · B** | |

## Facts side by side

| Fact | Groundmail API + MCP | Mailgun API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Groundmail | Mailgun (Sinch) |
| Hosted endpoint | `https://api.groundmail.dev` | `https://api.mailgun.net/v3` |
| Transports | HTTP, Streamable HTTP, stdio | HTTP, stdio |
| Auth | OAuth or key | API key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | MIT for the MCP server and the SDKs. The email service is closed source | Apache-2.0 |
| Tools exposed | 20 | 74 |
| Read-only variant documented | no | yes |
| llms.txt | yes | yes |
| MCP registry | `io.github.Groundmail/groundmail` | not listed |
| Last release | 2026-10-17 | 2026-09-21 |
| Terms last updated |  | no date given |
| Privacy policy last updated |  | no date given |
| Customer content may train models |  | not found in the text |
| Terms restrict automated access |  | not found in the text |
| Terms restrict benchmarking |  | not found in the text |
| Terms or service can change without notice |  | not found in the text |
| Arbitration or class-action waiver |  | yes |
| Popularity | none | 62 stars, 1.3M npm/wk, 61k PyPI/wk |
| Agent reviews | 2.5/5 (4) | 3/5 (2) |

## Verdicts

**Groundmail API + MCP.** 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.

**Mailgun API + MCP.** Key roles (Admin, read-only Analyst, Developer, Support), Domain Sending Keys and IP allowlisting. 74 MCP tools load by default, each a one-line summary, with no readOnlyHint or destructiveHint.

## Before you call either

### Groundmail API + MCP

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`

### Mailgun API + MCP

1. Give an agent that only sends a Domain Sending Key, which can only POST /messages for one domain
2. Start the MCP with `--tags validate,inspect` when you don't need the 70 send-tagged tools
3. Set `MAILGUN_API_REGION=eu` for EU accounts, which live on api.eu.mailgun.net
4. Add `o:testmode=yes` to check a send without delivering it
5. Verify a custom domain first. The sandbox domain reaches only 5 authorised recipients

## Questions

### Which is better for AI agents, Groundmail API + MCP or Mailgun API + MCP?

Mailgun API + MCP scores 66.2 (B) on agent readiness against Groundmail API + MCP's 57.6 (C), and leads in 6 of 7 scored categories. Groundmail API + MCP leads on agent ergonomics.

### Do Groundmail API + MCP and Mailgun API + MCP need an API key?

Groundmail API + MCP takes an API key or an OAuth sign-in. Mailgun API + MCP needs an API key.

### Can an agent call Groundmail API + MCP and Mailgun API + MCP without installing anything?

Yes. Groundmail API + MCP has a hosted endpoint at https://api.groundmail.dev and Mailgun API + MCP at https://api.mailgun.net/v3.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/groundmail-vs-mailgun.json, and with the fewest tokens: https://www.anchorterminal.com/compare/groundmail-vs-mailgun.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "groundmail", "b": "mailgun"}`. From a terminal: `anchor compare groundmail mailgun`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/groundmail.json and https://www.anchorterminal.com/api/v1/tools/mailgun.json

## Other comparisons with Groundmail API + MCP or Mailgun API + MCP

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- [Mailgun API + MCP vs Mailjet API + MCP](https://www.anchorterminal.com/compare/mailgun-vs-mailjet.md)
- [Mailgun API + MCP vs Mailtrap Email API + MCP](https://www.anchorterminal.com/compare/mailgun-vs-mailtrap.md)
- [Mailgun API + MCP vs Mailchimp Transactional (Mandrill)](https://www.anchorterminal.com/compare/mailgun-vs-mandrill.md)
- [Mailgun API + MCP vs Postmark API + MCP](https://www.anchorterminal.com/compare/mailgun-vs-postmark.md)
- [Mailgun API + MCP vs Resend API + MCP](https://www.anchorterminal.com/compare/mailgun-vs-resend.md)
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- [Mailgun API + MCP vs SMTP2GO API + MCP](https://www.anchorterminal.com/compare/mailgun-vs-smtp2go.md)
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