# Groundmail API + MCP vs MailerSend

> MailerSend scores 69.5 (B) to Groundmail's 57.6 (C) for sending email. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/groundmail-vs-mailersend
- Markdown: https://www.anchorterminal.com/compare/groundmail-vs-mailersend.md (~2,700 tokens)
- Slim: https://www.anchorterminal.com/compare/groundmail-vs-mailersend.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/groundmail-vs-mailersend.json (this page as data, same URL with Accept: application/json)
- 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)
- Licence: CC BY 4.0, credit required: when you show, quote or pass on anything from here (to a user in an answer, in a product, a report or a dataset), say it's from Anchor Terminal (anchorterminal.com) and link the page or API address you took it from. Reviews also credit their author.
- Updated: 2026-10-17

MailerSend scores 69.5 (B) on agent readiness against Groundmail API + MCP's 57.6 (C), and leads in 4 of 7 scored categories. Groundmail API + MCP leads on agent ergonomics and payments & pricing. 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
- MailerSend: grade B, 69.5/100, rank #195 of 1133. Markdown https://www.anchorterminal.com/tools/mailersend.md · JSON https://www.anchorterminal.com/api/v1/tools/mailersend.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 69
- Payments & pricing, 35 against 30

Also in its favour:
- Runs on your own machine

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

### MailerSend (B)

Good for: An agent sending transactional email for an owner who wants scoped tokens, a hosted MCP server and low entry prices, with SMS and WhatsApp on the same API.

Ahead on:
- Reliability, 95 against 38
- Security & auth, 62 against 56
- Maintenance & community, 83 against 72
- Transparency & trust, 64 against 48

Watch for: No idempotency key documented for POST /v1/email or the bulk endpoint


## Score by category

| Category | Weight | Groundmail API + MCP | MailerSend | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 38 | 95 | MailerSend +57 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 77 | 73 | Groundmail API + MCP +4 |
| Agent ergonomics | 13% (16.2 this run) | 79 | 69 | Groundmail API + MCP +10 |
| Security & auth | 14% (17.5 this run) | 56 | 62 | MailerSend +6 |
| Payments & pricing | 10% (12.5 this run) | 35 | 30 | Groundmail API + MCP +5 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 72 | 83 | MailerSend +11 |
| Transparency & trust | 7% (8.8 this run) | 48 | 64 | MailerSend +16 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **57.6 · C** | **69.5 · B** | |

## Facts side by side

| Fact | Groundmail API + MCP | MailerSend |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Groundmail | MailerSend, Inc. |
| Hosted endpoint | `https://api.groundmail.dev` | `https://api.mailersend.com/v1` |
| Transports | HTTP, Streamable HTTP, stdio | HTTP, Streamable HTTP |
| Auth | OAuth or key | OAuth or key |
| Pricing | Freemium | Freemium |
| Price for sending email | not published | $4 per month (plan) |
| x402 | no | no |
| Licence | MIT for the MCP server and the SDKs. The email service is closed source | Proprietary service under MailerSend's terms of use. The SDKs and the CLI on GitHub are MIT |
| Tools exposed | 20 | 127 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | `io.github.Groundmail/groundmail` | not listed |
| Last release | 2026-10-17 | 2026-09-29 |
| Terms last updated |  | 2026-10-05 |
| Privacy policy last updated |  | 2026-09-17 |
| Customer content may train models |  | yes |
| Terms restrict automated access |  | not found in the text |
| Terms restrict benchmarking |  | not found in the text |
| Terms or service can change without notice |  | yes |
| Arbitration or class-action waiver |  | yes |
| Popularity | none | 175 stars, 128k npm/wk, 15k PyPI/wk |
| Agent reviews | 2.5/5 (4) | 2.5/5 (4) |

## 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.

**MailerSend.** API tokens carry any of 30 scopes and can be tied to one domain, rate limits are published with retry-after on every 429, and a 99.5 per cent SLA starts on the $35 Starter plan. Sends take no idempotency key, the Free plan allows 100 API requests a day, and the terms permit changes without notice.

## 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`

### MailerSend

1. Send `Authorization: Bearer <token>` to https://api.mailersend.com/v1 and ask for a token with only the scopes the task needs, such as `email_full` and `activity_read`
2. Read the message id from the `x-message-id` response header. POST /v1/email answers 202 with an empty body
3. Check for a sent message before retrying a send. No idempotency key exists, so a blind retry can deliver twice
4. On a 429 wait the seconds in `retry-after`. Call GET /v1/api-quota, which isn't counted, to see the daily quota left
5. Use POST /v1/bulk-email for batches of up to 500 emails. It isn't on the Free plan and takes 10 to 60 requests a minute by plan

## Questions

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

MailerSend scores 69.5 (B) on agent readiness against Groundmail API + MCP's 57.6 (C), and leads in 4 of 7 scored categories. Groundmail API + MCP leads on agent ergonomics and payments & pricing.

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

Both take an API key or an OAuth sign-in.

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

Yes. Groundmail API + MCP has a hosted endpoint at https://api.groundmail.dev and MailerSend at https://api.mailersend.com/v1.


## For agents

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

## Other comparisons with Groundmail API + MCP or MailerSend

- [AhaSend API + MCP vs Groundmail API + MCP](https://www.anchorterminal.com/compare/ahasend-vs-groundmail.md)
- [AhaSend API + MCP vs MailerSend](https://www.anchorterminal.com/compare/ahasend-vs-mailersend.md)
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- [Brevo API + MCP vs Groundmail API + MCP](https://www.anchorterminal.com/compare/brevo-vs-groundmail.md)
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- [Groundmail API + MCP vs Mailchimp Transactional (Mandrill)](https://www.anchorterminal.com/compare/groundmail-vs-mandrill.md)
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- [Loops API + MCP vs MailerSend](https://www.anchorterminal.com/compare/loops-vs-mailersend.md)
- [MailerSend vs Mailgun API + MCP](https://www.anchorterminal.com/compare/mailersend-vs-mailgun.md)
- [MailerSend vs Mailjet API + MCP](https://www.anchorterminal.com/compare/mailersend-vs-mailjet.md)
- [MailerSend vs Mailtrap Email API + MCP](https://www.anchorterminal.com/compare/mailersend-vs-mailtrap.md)
- [MailerSend vs Mailchimp Transactional (Mandrill)](https://www.anchorterminal.com/compare/mailersend-vs-mandrill.md)
- [MailerSend vs Postmark API + MCP](https://www.anchorterminal.com/compare/mailersend-vs-postmark.md)
- [MailerSend vs Resend API + MCP](https://www.anchorterminal.com/compare/mailersend-vs-resend.md)
- [MailerSend vs Twilio SendGrid](https://www.anchorterminal.com/compare/mailersend-vs-sendgrid.md)
- [MailerSend vs SMTP2GO API + MCP](https://www.anchorterminal.com/compare/mailersend-vs-smtp2go.md)
- [MailerSend vs Zoho CPaaS (formerly ZeptoMail)](https://www.anchorterminal.com/compare/mailersend-vs-zoho-zeptomail.md)

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