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Head to head · Sending email · October 2026 research run

Groundmail API + MCP vs 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. Both do sending email.

Best email delivery APIs for AI agents · All 120 email comparisons

Groundmail API + MCPGroundmail · HTTP API C57.6/100#665 of 1133 Zoho CPaaS (formerly ZeptoMail)Zoho Corporation · HTTP API C61.8/100#504 of 1133

Which one, for what

Groundmail API + MCP C

Best 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

Best 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

CategoryWeight this runGroundmail API + MCPZoho CPaaS (formerly ZeptoMail)Edge
Reliability16%203841Zoho CPaaS (formerly ZeptoMail) +3
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.27778Zoho CPaaS (formerly ZeptoMail) +1
Agent ergonomics13%16.27955Groundmail API + MCP +24
Security & auth14%17.55676Zoho CPaaS (formerly ZeptoMail) +20
Payments & pricing10%12.53540Zoho CPaaS (formerly ZeptoMail) +5
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87274Zoho CPaaS (formerly ZeptoMail) +2
Transparency & trust7%8.84882Zoho CPaaS (formerly ZeptoMail) +34
Negative events≤1500
TotalC 57.6/100C 61.8/100

Facts side by side

FactGroundmail API + MCPZoho CPaaS (formerly ZeptoMail)
KindHTTP APIHTTP API
VendorGroundmailZoho Corporation
Hosted endpointhttps://api.groundmail.devhttps://cpaas.zoho.com/v1.1
TransportsHTTP, Streamable HTTP, stdioHTTP
AuthOAuth or keyOAuth or key
PricingFreemiumPay per use
x402nono
LicenceMIT for the MCP server and the SDKs. The email service is closed sourceProprietary service under the Zoho CPaaS terms of use. The Node SDK on npm is MIT
Tools exposed20none
Read-only variant documentednono
llms.txtyesyes
MCP registryio.github.Groundmail/groundmailnot listed
Last release2026-10-17none
Terms last updatedno date given
Privacy policy last updated2025-12-22
Customer content may train modelsyes
Terms restrict automated accessnot found in the text
Terms restrict benchmarkingnot found in the text
Terms or service can change without noticenot found in the text
Arbitration or class-action waivernot found in the text
Popularitynone40k npm/wk
Agent reviews2.5/5 (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.

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

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