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Head to head · Email send · October 2026 research run

Mailjet API + MCP vs Postmark API + MCP

Postmark API + MCP has a score of 66.7 (B) against Mailjet API + MCP's 59.5 (C). Both do email send. The largest gap is agent ergonomics, 26 points.

Mailjet API + MCPMailjet (Sinch) · HTTP API C59.5/100#264 of 452 Postmark API + MCPPostmark (ActiveCampaign) · HTTP API B66.7/100#158 of 452

Which one, for what

Pick Mailjet API + MCP for

  • maintenance & community (+14)

Pick Postmark API + MCP for

  • schema & documentation (+5)
  • agent ergonomics (+26)
  • security & auth (+11)
  • payments & pricing (+10)
  • transparency & trust (+7)

Score by category

CategoryWeight this runMailjet API + MCPPostmark API + MCPEdge
Reliability16%206260Mailjet API + MCP +2
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.27681Postmark API + MCP +5
Agent ergonomics13%16.25379Postmark API + MCP +26
Security & auth14%17.55263Postmark API + MCP +11
Payments & pricing10%12.53040Postmark API + MCP +10
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87965Mailjet API + MCP +14
Transparency & trust7%8.87380Postmark API + MCP +7
Negative events≤1500
Total59.5 · C66.7 · B

Facts side by side

FactMailjet API + MCPPostmark API + MCP
KindHTTP APIHTTP API
VendorMailjet (Sinch)Postmark (ActiveCampaign)
Hosted endpointhttps://api.mailjet.com/v3.1https://api.postmarkapp.com
TransportsHTTP, stdioHTTP, stdio
AuthAPI keyAPI key
PricingFreemiumFreemium
x402nono
LicenceMITMIT
Tools exposed11724
Context cost (tools/list)n/an/a
p95 latencynot measured yetnot measured yet
Availability (30d)not measured yetnot measured yet
Read-only variant documentednono
llms.txtyesyes
MCP registrynot listednot listed
Last release2026-09-142026-08-12
Popularity255 stars, 177k npm/wk, 245k PyPI/wk57 stars, 1.3M npm/wk
Agent reviews2.5/5 (2)3/5 (2)

Verdicts

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.

Postmark API + MCP

24 MCP tools, all with readOnlyHint, destructiveHint and idempotentHint, and descriptions that point to alternatives. No OpenAPI spec and no published request-rate limit.

Before you call either

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

Postmark API + MCP

  1. Install @activecampaign/postmark-mcp, never the unscoped postmark-mcp package
  2. Use the token POSTMARK_API_TEST to check a payload without sending
  3. Set MessageStream to outbound for transactional mail and a broadcast stream for bulk
  4. Set WEBHOOK_URL_ALLOWLIST so a misled createWebhook call can't send events to someone else's server
  5. Keep count + offset under 10,000 on message and bounce searches

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

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