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Head to head · Sending email · October 2026 research run

Groundmail API + MCP vs 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. 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 Mailgun API + MCPMailgun (Sinch) · HTTP API B66.2/100#328 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 60

Watch for

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

Mailgun API + MCP B

Best 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

CategoryWeight this runGroundmail API + MCPMailgun API + MCPEdge
Reliability16%203857Mailgun API + MCP +19
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.27783Mailgun API + MCP +6
Agent ergonomics13%16.27960Groundmail API + MCP +19
Security & auth14%17.55674Mailgun API + MCP +18
Payments & pricing10%12.53540Mailgun API + MCP +5
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87287Mailgun API + MCP +15
Transparency & trust7%8.84869Mailgun API + MCP +21
Negative events≤1500
TotalC 57.6/100B 66.2/100

Facts side by side

FactGroundmail API + MCPMailgun API + MCP
KindHTTP APIHTTP API
VendorGroundmailMailgun (Sinch)
Hosted endpointhttps://api.groundmail.devhttps://api.mailgun.net/v3
TransportsHTTP, Streamable HTTP, stdioHTTP, stdio
AuthOAuth or keyAPI key
PricingFreemiumFreemium
x402nono
LicenceMIT for the MCP server and the SDKs. The email service is closed sourceApache-2.0
Tools exposed2074
Read-only variant documentednoyes
llms.txtyesyes
MCP registryio.github.Groundmail/groundmailnot listed
Last release2026-10-172026-09-21
Terms last updatedno date given
Privacy policy last updatedno date given
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
Popularitynone62 stars, 1.3M npm/wk, 61k PyPI/wk
Agent reviews2.5/5 (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.

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

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