Mailjet API + MCP (2026): v3 REST, v3.1 send, read-only MCP

Mailjet runs two API versions side by side and they are not interchangeable: v3 is the REST platform for every non-send resource, v3.1 exists only for the Send API. Authentication is HTTPS Basic Auth with the same key pair that powers the SMTP settings, and Mailjet ships 7 official SDKs plus an EU-resident API host at api.eu.mailjet.com. On MCP it is ahead of the field — a first-party server since September 30, 2025 — but read-only, so an agent can interrogate your account and cannot send from it.

At a glance

MCP integration in 2026

MCP is how an AI client reaches into a SaaS account without a bespoke plugin. For an ESP the question is not whether a wrapper exists on GitHub, but whether the vendor ships one and what it may do.

Available MCP servers

Three of the four below are Mailjet’s own material; the fourth is Zapier’s hosted endpoint, the only route offering write actions.

Mailjet API essentials

The version split is the first thing to internalise: everything that is not a send — contacts, lists, campaigns, templates, statistics, senders, DNS, webhooks, parse routes — lives at /v3/REST/ and always will.

Limit defaults to 10, so a first call to /v3/REST/contact returns ten records and an integrator concludes the account is nearly empty. Raise it to 1000, read Total from the envelope, and increment Offset until you have the lot. There is no cursor pagination, so the client owns the loop. Mailjet publishes no HTTP request timeout, so set your own client-side deadline.

Authentication methods

HTTPS Basic Auth (API Key and Secret Key)

Every Email API endpoint authenticates with HTTPS Basic Auth: username is your API Key (public), password your Secret Key (private), both under Account settings › SMTP and SEND API settings. The relay at in-v3.mailjet.com expects the same pair, so rotating a key breaks both transports at once — plan it with your SMTP settings open. All seven SDKs read it from MJ_APIKEY_PUBLIC and MJ_APIKEY_PRIVATE.

API tokens for the IFrame API

The /v3/REST/apitoken resource issues short-lived tokens for embedding Mailjet UI components in your own product. Scoped to that job — not a replacement for Basic Auth, and not a way to give a partner limited access.

Additional API keys for isolation

Another key from /v3/REST/apikey is how Mailjet does sub-accounts: separating transactional from marketing, or ring-fencing staging. Deactivate with IsActive: false on a PUT rather than deleting; per-key lifetime usage is at /v3/REST/apikeytotals.

Rate limits

Mailjet is unusually sparse here. The honest table has more blanks than most competitors would like; what follows is only what Mailjet publishes.

The workaround is empirical: ramp deliberately, instrument for HTTP 429 and SMTP deferrals, and back off exponentially. Mailjet tells new customers to demonstrate good performance over at least one week before the initial hourly limit lifts, which gives the shape of the ramp if not the number. If you need a published requests-per-second figure, Postmark and MailerSend are more forthcoming.

Official SDKs

Seven wrappers are published under the github.com/mailjet organisation. All share one design: construct a client with the key pair, set the API version at client level, then call resources.

Notable community SDKs

Because the API is Basic Auth over JSON with no signing step, the framework ecosystem reaches Mailjet through generic mail transports rather than dedicated third-party SDKs: Symfony and Laravel through their mailer abstractions, Rails through the official gem’s ActionMailer hook. For anything else, write forty lines against the REST endpoints rather than adopting an unofficial wrapper that may be abandoned.

Endpoints reference

The fifteen resources below carry almost all real integration traffic. Full reference: Mailjet’s Email API reference and the open-source api-documentation repo, often easier to read because the portal renders client-side.

Reporting sits in a family of resources rather than one endpoint: /v3/REST/statcounters is the general aggregator, while geostatistics, openinformation, clickstatistics, bouncestatistics and statistics/recipient-esp break the data out by country, user agent, click URL and mailbox provider.

Code examples

Sending with the Python SDK

# pip install mailjet-rest
import os
from mailjet_rest import Client

# version='v3.1' selects the current Send API. Omit it and you get the v3
# endpoint, which expects a different payload shape entirely.
mailjet = Client(
    auth=(os.environ['MJ_APIKEY_PUBLIC'], os.environ['MJ_APIKEY_PRIVATE']),
    version='v3.1',
)

data = {'Messages': [{
    'From': {'Email': 'no-reply@yourdomain.com', 'Name': 'Your App'},
    'To': [{'Email': 'customer@example.com', 'Name': 'Customer'}],
    'Subject': 'Your receipt',
    'TextPart': 'Thanks for your order.',
    'HTMLPart': '<h3>Thanks for your order.</h3>',
    'CustomID': 'order-1234',
}]}

result = mailjet.send.create(data=data)
print(result.status_code, result.json())

# EU residency: add api_url='https://api.eu.mailjet.com/' to Client().

Sending with the Node.js SDK

// npm install node-mailjet
const Mailjet = require('node-mailjet');

const mailjet = Mailjet.apiConnect(
  process.env.MJ_APIKEY_PUBLIC,
  process.env.MJ_APIKEY_PRIVATE,
);

// { version: 'v3.1' } is required - the default is v3, whose payload
// uses FromEmail / Html-part, not From / HTMLPart.
mailjet
  .post('send', { version: 'v3.1' })
  .request({
    Messages: [{
      From: { Email: 'no-reply@yourdomain.com', Name: 'Your App' },
      To: [{ Email: 'customer@example.com', Name: 'Customer' }],
      Subject: 'Your receipt',
      TextPart: 'Thanks for your order.',
      HTMLPart: '<h3>Thanks for your order.</h3>',
      CustomID: 'order-1234',
    }],
  })
  .then((result) => console.log(result.body))
  .catch((err) => console.log(err.statusCode, err.message));

Handling batched Event API webhooks

Mailjet groups every event of the last second for one webhook URL into a single POST, so the body is an array of mixed event types. Iterate, always.

app.post('/webhooks/mailjet', express.json(), (req, res) => {
  // ALWAYS an array. A single-object handler passes in testing and
  // breaks the moment batching kicks in under real traffic.
  const events = Array.isArray(req.body) ? req.body : [req.body];

  for (const e of events) {
    // e.event: sent | open | click | bounce | spam | blocked | unsub
    enqueue({
      type: e.event,
      email: e.email,
      at: new Date(e.time * 1000),
      messageId: e.MessageID,
      correlation: e.CustomID,   // set at send time
    });
  }

  // Return 200 fast. A non-200 is retried every 30 seconds for 24 hours.
  res.sendStatus(200);
});

Common gotchas

Deprecations and changelog

• September 9, 2026 (forward-dated) — subscription pricing update takes effect, affecting pricing only — no change to plans, packaging or entitlements. Essential 15k moves to $19.00, Premium 15k to $29.00; Starter holds at $9.00.
• February 3, 2026 — Advanced Automations and AI Segmentation shipped together. Automations trigger journeys from opens, clicks, purchases or sign-ups and allow editing a live workflow without interrupting it; AI Segmentation turns a plain-language description into a segment.
• November 4, 2025 — Custom Unsubscribe Manager and Preference Center released, replacing all-or-nothing opt-out with branded pages where subscribers pick content types and frequency.
• October 6, 2025 — free plan changes took effect: free accounts capped at 1,000 contacts, templates no longer downloadable on free accounts.
• September 30, 2025 — the official Mailjet MCP Server was released, open-source and read-only.

Nothing here is formally deprecated: /v3/send remains live with no published sunset date, but new transactional work belongs on /v3.1/send. Track changes at Mailjet’s official release notes.

Frequently asked questions