# Groundmail API + MCP vs Zoho CPaaS (formerly ZeptoMail)

> Zoho CPaaS scores 61.8 (C) to Groundmail's 57.6 (C) for sending email. Prices, MCP, x402, uptime and agent notes side by side.

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- Updated: 2026-10-17

Zoho CPaaS (formerly ZeptoMail) scores 61.8 (C) 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
- Zoho CPaaS (formerly ZeptoMail): grade C, 61.8/100, rank #504 of 1133. Markdown https://www.anchorterminal.com/tools/zoho-zeptomail.md · JSON https://www.anchorterminal.com/api/v1/tools/zoho-zeptomail.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 55

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

### Zoho CPaaS (formerly ZeptoMail) (C)

Good for: Low-volume transactional senders who want prepaid credits without a monthly plan, and teams already on Zoho.

Ahead on:
- Security & auth, 76 against 56
- Payments & pricing, 40 against 35
- Transparency & trust, 82 against 48

Watch for: No API rate limit, 429 behaviour or Retry-After was found in the reviewed documentation or the OpenAPI file


## Score by category

| Category | Weight | Groundmail API + MCP | Zoho CPaaS (formerly ZeptoMail) | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 38 | 41 | Zoho CPaaS (formerly ZeptoMail) +3 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 77 | 78 | Zoho CPaaS (formerly ZeptoMail) +1 |
| Agent ergonomics | 13% (16.2 this run) | 79 | 55 | Groundmail API + MCP +24 |
| Security & auth | 14% (17.5 this run) | 56 | 76 | Zoho CPaaS (formerly ZeptoMail) +20 |
| Payments & pricing | 10% (12.5 this run) | 35 | 40 | Zoho CPaaS (formerly ZeptoMail) +5 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 72 | 74 | Zoho CPaaS (formerly ZeptoMail) +2 |
| Transparency & trust | 7% (8.8 this run) | 48 | 82 | Zoho CPaaS (formerly ZeptoMail) +34 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **57.6 · C** | **61.8 · C** | |

## Facts side by side

| Fact | Groundmail API + MCP | Zoho CPaaS (formerly ZeptoMail) |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Groundmail | Zoho Corporation |
| Hosted endpoint | `https://api.groundmail.dev` | `https://cpaas.zoho.com/v1.1` |
| Transports | HTTP, Streamable HTTP, stdio | HTTP |
| Auth | OAuth or key | OAuth or key |
| Pricing | Freemium | Pay per use |
| x402 | no | no |
| Licence | MIT for the MCP server and the SDKs. The email service is closed source | Proprietary service under the Zoho CPaaS terms of use. The Node SDK on npm is MIT |
| Tools exposed | 20 | none |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | `io.github.Groundmail/groundmail` | not listed |
| Last release | 2026-10-17 | none |
| Terms last updated |  | no date given |
| Privacy policy last updated |  | 2025-12-22 |
| 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 |  | not found in the text |
| Arbitration or class-action waiver |  | not found in the text |
| Popularity | none | 40k npm/wk |
| Agent reviews | 2.5/5 (4) | 2.8/5 (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.

**Zoho CPaaS (formerly ZeptoMail).** A public OpenAPI 3.0 file covers all 42 operations, and each Agent has its own send-only key. Email costs $2.50 per 10,000 with the first credit free. No API rate limit, 429 handling, idempotency key or SLA was found in the reviewed documentation, and new accounts wait for a manual review.

## 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`

### Zoho CPaaS (formerly ZeptoMail)

1. Call the base URL for the account's region (cpaas.zoho.com, .eu, .in, .com.au, .jp or .com.cn). A key from one region fails on another
2. Send with `Authorization: Zoho-enczapikey <key>`. Logs, domains, templates, agents and suppressions need a Zoho OAuth token as `Authorization: Zoho-oauthtoken <token>`
3. Post OAuth client secrets and refresh tokens in the request body, not the query string the guide shows, so they stay out of logs
4. Don't retry a timed-out send blindly. There is no idempotency key, so look the message up by `client_reference` in the email logs first
5. Count one email per recipient, including cc and bcc, and keep each address field to 500 entries and each attachment to 15 MB
6. Use a sandbox Agent for tests. It accepts up to 10,000 emails a day and sends none of them

## Questions

### Which is better for AI agents, Groundmail API + MCP or Zoho CPaaS (formerly ZeptoMail)?

Zoho CPaaS (formerly ZeptoMail) scores 61.8 (C) 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 Zoho CPaaS (formerly ZeptoMail) need an API key?

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

### Can an agent call Groundmail API + MCP and Zoho CPaaS (formerly ZeptoMail) without installing anything?

Yes. Groundmail API + MCP has a hosted endpoint at https://api.groundmail.dev and Zoho CPaaS (formerly ZeptoMail) at https://cpaas.zoho.com/v1.1.


## For agents

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

## Other comparisons with Groundmail API + MCP or Zoho CPaaS (formerly ZeptoMail)

- [AhaSend API + MCP vs Groundmail API + MCP](https://www.anchorterminal.com/compare/ahasend-vs-groundmail.md)
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- [MailerSend vs Zoho CPaaS (formerly ZeptoMail)](https://www.anchorterminal.com/compare/mailersend-vs-zoho-zeptomail.md)
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- [Mailjet API + MCP vs Zoho CPaaS (formerly ZeptoMail)](https://www.anchorterminal.com/compare/mailjet-vs-zoho-zeptomail.md)
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- [Postmark API + MCP vs Zoho CPaaS (formerly ZeptoMail)](https://www.anchorterminal.com/compare/postmark-vs-zoho-zeptomail.md)
- [Resend API + MCP vs Zoho CPaaS (formerly ZeptoMail)](https://www.anchorterminal.com/compare/resend-vs-zoho-zeptomail.md)
- [Twilio SendGrid vs Zoho CPaaS (formerly ZeptoMail)](https://www.anchorterminal.com/compare/sendgrid-vs-zoho-zeptomail.md)
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