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Mailack documentation.

Quickstart, product API and SDKs. Certified email with NOM-151 evidence, exposed as HTTP API and MCP.

API key → send → status → proof-bundle → verify → MCP

Guides
start here

Quickstart

API key, first message, status, proof bundle, offline verify and MCP.

POST /v1/domains

Sending domains

Register your domain, publish the TXT challenge and verify From.

email.*

Webhooks

Lifecycle events signed with Mailack-Signature (HMAC-SHA256).

{{var}}

Templates

Subject and body with {{variables}} and send via template_id.

/v1/messages/batch · /v1/rates

API: batch, rates and errors

Bulk ingest, deliverability dashboard and error codes.

official clients

SDKs

Go, Rust, JavaScript, Node/TS, Python, Java and C#.

screen guide

Client portal

Dashboard, keys, messages, evidence and billing in the UI.

Gmail

Chrome extension

Send NOM-151 certified email from the Gmail compose window, with tracking and proof.

  1. 01environment variables

    Authenticate with an API key

    Export the portal key (mlk_ prefix). Every machine /v1/* route requires Authorization: Bearer. The tenant is resolved on the server from the key.

    environment variables
    export MAILACK_API_KEY="mlk_..."
export MAILACK_API_URL="https://api.mailack.com"

# Cada petición lleva la clave en Authorization.
curl -s "$MAILACK_API_URL/v1/messages" \
  -H "Authorization: Bearer $MAILACK_API_KEY" \
  -H "Accept: application/json"
  2. 02POST /v1/messages

    Send the first message

    POST /v1/messages with Idempotency-Key. Keep the id from the response for later steps. Retrying with the same key is safe (replay).

    POST /v1/messages
    MESSAGE_ID=$(curl -s -X POST "$MAILACK_API_URL/v1/messages" \
  -H "Authorization: Bearer $MAILACK_API_KEY" \
  -H "Idempotency-Key: $(uuidgen)" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "noreply@acme.mx",
    "to": "cliente@ejemplo.com",
    "subject": "Primer mensaje",
    "html": "<p>Hola desde mailack.</p>"
  }' | jq -r .id)

echo "$MESSAGE_ID"
  3. 03GET /v1/messages/{id}

    Check its status

    GET /v1/messages/{id} returns delivery status, events and message metadata.

    GET /v1/messages/{id}
    curl -s "$MAILACK_API_URL/v1/messages/$MESSAGE_ID" \
  -H "Authorization: Bearer $MAILACK_API_KEY" | jq .
  4. 04GET /v1/messages/{id}/proof-bundle

    Download the proof bundle

    GET /v1/messages/{id}/proof-bundle. Includes the canonical hash, Merkle inclusion proof and, when present, the PSC Codex certificate.

    GET /v1/messages/{id}/proof-bundle
    curl -s "$MAILACK_API_URL/v1/messages/$MESSAGE_ID/proof-bundle" \
  -H "Authorization: Bearer $MAILACK_API_KEY" \
  -o bundle.json

# Campos de la constancia del PSC Codex en el bundle:
# certificate_id, serial_number, policy_oid, algorithm_oid, sealed_at
jq '{certificate_id, serial_number, sealed_at}' bundle.json
  5. 05POST /v1/verify

    Verify it

    POST /v1/verify recomputes the Merkle inclusion proof and answers valid: true|false. And without an account, anyone can check the bundle at mailack.com/verificar: the check runs in their browser and the file never leaves their device.

    POST /v1/verify
    curl -s -X POST "$MAILACK_API_URL/v1/verify" \
  -H "Authorization: Bearer $MAILACK_API_KEY" \
  -H "Content-Type: application/json" \
  -d "{\"message_id\": \"$MESSAGE_ID\"}" | jq .
# → {"valid": true, "merkle_root": "…", "certificate_id": "…", "sealed_at": "…"}

# Sin cuenta: bundle.json en mailack.com/verificar (todo en el navegador)
  6. 06mcpServers.mailack

    Connect the MCP server

    Register mailack-mcp in your MCP client. The agent can send, query, verify and manage domains/webhooks through the exposed tools.

    mcpServers.mailack
    {
  "mcpServers": {
    "Mailack": {
      "command": "./bin/mailack-mcp",
      "env": {
        "MAILACK_API_KEY": "mlk_...",
        "MAILACK_API_URL": "https://api.mailack.com"
      }
    }
  }
}

OpenAPI reference

The formal contract lives in the Mailack repository (docs/openapi.yaml). These pages are the product guide and the shortest path to a first verified proof bundle.