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Head to head · Sending email · October 2026 research run

Groundmail API + MCP vs Mailjet API + MCP

Mailjet API + MCP scores 59.4 (C) on agent readiness against Groundmail API + MCP's 57.6 (C), and leads in 3 of 7 scored categories. Groundmail API + MCP leads on agent ergonomics and payments & pricing. 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 Mailjet API + MCPMailjet (Sinch) · HTTP API C59.4/100#604 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 53
  • Payments & pricing, 35 against 30

Watch for

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

Mailjet API + MCP C

Best for EU-based senders who want cheap transactional and marketing mail with data kept in the EU.

Ahead on

  • Reliability, 62 against 38
  • Maintenance & community, 79 against 72
  • Transparency & trust, 72 against 48

Also in its favour

  • Free to start without a card

Watch for

The MCP server registers 117 GET-only tools and can't send

Score by category

CategoryWeight this runGroundmail API + MCPMailjet API + MCPEdge
Reliability16%203862Mailjet API + MCP +24
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.27776Groundmail API + MCP +1
Agent ergonomics13%16.27953Groundmail API + MCP +26
Security & auth14%17.55652Groundmail API + MCP +4
Payments & pricing10%12.53530Groundmail API + MCP +5
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87279Mailjet API + MCP +7
Transparency & trust7%8.84872Mailjet API + MCP +24
Negative events≤1500
TotalC 57.6/100C 59.4/100

Facts side by side

FactGroundmail API + MCPMailjet API + MCP
KindHTTP APIHTTP API
VendorGroundmailMailjet (Sinch)
Hosted endpointhttps://api.groundmail.devhttps://api.mailjet.com/v3.1
TransportsHTTP, Streamable HTTP, stdioHTTP, stdio
AuthOAuth or keyAPI key
PricingFreemiumFreemium
x402nono
LicenceMIT for the MCP server and the SDKs. The email service is closed sourceMIT
Tools exposed20117
Read-only variant documentednono
llms.txtyesyes
MCP registryio.github.Groundmail/groundmailnot listed
Last release2026-10-172026-09-14
Terms last updatedno date given
Privacy policy last updated2026-09-29
Customer content may train modelsnot found in the text
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 waiveryes
Popularitynone255 stars, 177k npm/wk, 245k PyPI/wk
Agent reviews2.5/5 (4)2.5/5 (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.

Mailjet API + MCP

SandboxMode on Send API v3.1 validates a payload without delivering it. The MCP server registers 117 GET-only tools and can't send.

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

Mailjet API + MCP

  1. Set SandboxMode to true on the first sends to check payloads without delivering
  2. Send with POST /v3.1/send and a Messages array, many messages per call
  3. Use the MCP for statistics and contact lookups only, since it can't send
  4. Pass MAILJET_API_KEY as key:secret. The server checks it at startup and exits if it's wrong
  5. On 429, wait and retry. Non-transactional endpoints have much lower limits than send

Questions

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

Mailjet API + MCP scores 59.4 (C) on agent readiness against Groundmail API + MCP's 57.6 (C), and leads in 3 of 7 scored categories. Groundmail API + MCP leads on agent ergonomics and payments & pricing.

Do Groundmail API + MCP and Mailjet API + MCP need an API key?

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

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

Yes. Groundmail API + MCP has a hosted endpoint at https://api.groundmail.dev and Mailjet API + MCP at https://api.mailjet.com/v3.1.

Other comparisons with Groundmail API + MCP or Mailjet API + MCP

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