Transactional email API

Send an email

POST to https://mail.flinkk.io/api/v1/emails with your API key as a bearer token. Create keys under Developer Settings; each key is tied to one domain and is shown once. The response is the email id.

curl -X POST https://mail.flinkk.io/api/v1/emails \
  -H "Authorization: Bearer $FLINKK_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "Acme <hello@yourdomain.com>",
    "to": ["customer@example.com"],
    "subject": "Welcome aboard",
    "html": "<p>Glad you are here.</p>"
  }'

const res = await fetch('https://mail.flinkk.io/api/v1/emails', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json', Authorization: 'Bearer ' + process.env.FLINKK_API_KEY },
  body: JSON.stringify({
    from: 'Acme <hello@yourdomain.com>',
    to: ['customer@example.com'],
    subject: 'Welcome aboard',
    html: '<p>Glad you are here.</p>',
  }),
});
console.log(await res.json()); // { id: '...' }

import os, requests

res = requests.post(
    "https://mail.flinkk.io/api/v1/emails",
    headers={"Authorization": f"Bearer {os.environ['FLINKK_API_KEY']}"},
    json={
        "from": "Acme <hello@yourdomain.com>",
        "to": ["customer@example.com"],
        "subject": "Welcome aboard",
        "html": "<p>Glad you are here.</p>",
    },
)
print(res.json())  # {"id": "..."}

POST /api/v1/emails/batch sends up to 100 emails in one request (all are validated first, so a bad item sends nothing), and GET /api/v1/emails/{id} returns the email with its latest delivery status. The full contract is in the OpenAPI 3.1 spec at /openapi-email.json.

Each key is limited to 120 requests a minute, and each workspace has a daily sending limit (100 emails a day by default). Over either limit the API answers 429, with Retry-After for the rate limit, rather than silently dropping mail. The original endpoint, /api/client/email/send with an api-key header, keeps working.

Your own domain, DKIM and custom MAIL FROM

Add your domain in Flinkk Mail and publish the DNS records it shows you. Flinkk Mail creates the sending identity in Amazon SES with DKIM signing and a custom MAIL FROM subdomain, so your mail is authenticated as coming from your domain instead of a shared one. Add as many sending addresses on the domain as you need and choose which team members may use each one.

Delivery tracking and webhooks

Delivered, bounced, complained, opened and clicked events are recorded for every message and shown in Logs. To get them in your own system, add a webhook endpoint under Agents, Webhooks. Flinkk Mail sends email.sent, email.delivered and email.bounced (and email.received for inbound mail) as signed JSON, with retries.

Payloads contain ids and metadata only. Verification code for Node and Python is in the agent API docs.

Receiving mail, and the v1 inbox API

Replies and inbound mail land in a shared, threaded inbox your team can read. The same inbox is available to software through the versioned REST API under /api/v1 (list inboxes and threads, read messages as clean text, search, draft and send replies, label and archive) and through a hosted MCP server, with scopes and human approval for agents.

curl https://mail.flinkk.io/api/v1/inboxes \
  -H "Authorization: Bearer $FLINKK_AGENT_KEY"

Frequently asked questions