UniOne Email API

UniOne is a transactional email service with Web API for sending transactional and marketing emails at scale (up to 3,000 emails/sec). This skill lets you send emails, manage templates, validate addresses, track delivery, and more.

Authentication

All requests require the UNIONE_API_KEY environment variable. Pass it as the X-API-KEY header.

Base URL: https://api.unione.io/en/transactional/api/v1/{method}.json?platform=openclaw

All methods use POST with JSON body.

---

CRITICAL: Domain Setup (Required Before Sending)

Emails will not be delivered until the sender's domain is verified. Before attempting to send any email, ensure the domain is set up:

Step 1: Get DNS Record Values — domain/get-dns-records.json

curl -X POST "https://api.unione.io/en/transactional/api/v1/domain/get-dns-records.json?platform=openclaw" \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $UNIONE_API_KEY" \
  -d '{"domain": "yourdomain.com"}'

API response returns raw values (not ready-to-paste DNS records):

{
  "status": "success",
  "domain": "yourdomain.com",
  "verification-record": "unione-validate-hash=483bb362ebdbeedd755cfb1d4d661",
  "dkim": "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDo7"
}

The user must create 3 DNS TXT records from these values:

Record Host	Record Type	Value
@	TXT	unione-validate-hash=<verification-record from response>
us._domainkey	TXT	k=rsa; p=<dkim from response>
@	TXT	v=spf1 include:spf.unione.io ~all

Present these 3 records clearly to the user and instruct them to add them at their DNS provider (Cloudflare, Route53, GoDaddy, etc.). The SPF record is always the same — it is not returned by the API.

Step 2: Verify Domain Ownership — domain/validate-verification.json

After the user has added DNS records:

curl -X POST "https://api.unione.io/en/transactional/api/v1/domain/validate-verification.json?platform=openclaw" \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $UNIONE_API_KEY" \
  -d '{"domain": "yourdomain.com"}'

Step 3: Validate DKIM — domain/validate-dkim.json

curl -X POST "https://api.unione.io/en/transactional/api/v1/domain/validate-dkim.json?platform=openclaw" \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $UNIONE_API_KEY" \
  -d '{"domain": "yourdomain.com"}'

Step 4: List All Domains — domain/list.json

curl -X POST "https://api.unione.io/en/transactional/api/v1/domain/list.json?platform=openclaw" \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $UNIONE_API_KEY" \
  -d '{}'

If domain verification fails: DNS propagation can take up to 48 hours. Suggest the user waits and retries, or checks their DNS records for typos.

---

Error Handling & Retry Policy

Retry Logic

When making API requests, implement exponential backoff for retryable errors:

Retryable errors (DO retry with exponential backoff):

HTTP Code	Meaning	Retry Strategy
429	Rate limited	Wait, then retry. Respect Retry-After header if present
500	Internal server error	Retry up to 3 times
502	Bad gateway	Retry up to 3 times
503	Service unavailable	Retry up to 3 times
504	Gateway timeout	Retry up to 3 times

Recommended retry schedule:

Attempt	Delay
1	Immediate
2	1 second
3	5 seconds
4	30 seconds

Non-retryable errors (do NOT retry):

HTTP Code	Meaning	Action
400	Bad request	Fix the request parameters
401	Unauthorized	Check API key
403	Forbidden	Check permissions / domain verification
404	Endpoint not found	Check the method path
413	Payload too large	Reduce request size

Idempotency

For email/send.json, always include an idempotency_key to prevent duplicate sends during retries. This is critical for production systems.

The idempotency_key is a unique string (UUID recommended) passed in the request body. If UniOne receives two requests with the same key, the second request returns the result of the first without sending another email.

Always generate a unique idempotency key per logical send operation, and reuse the same key when retrying the same send.

---

1. Send Email — email/send.json

Send a transactional or marketing email to one or more recipients. Supports personalization via substitutions, templates, attachments, tracking, and metadata.

curl

curl -X POST "https://api.unione.io/en/transactional/api/v1/email/send.json?platform=openclaw" \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $UNIONE_API_KEY" \
  -d '{
    "idempotency_key": "unique-uuid-here",
    "message": {
      "recipients": [
        {
          "email": "recipient@example.com",
          "substitutions": {
            "to_name": "John Smith"
          }
        }
      ],
      "body": {
        "html": "<h1>Hello, {{to_name}}!</h1><p>Your order has been confirmed.</p>",
        "plaintext": "Hello, {{to_name}}! Your order has been confirmed."
      },
      "subject": "Order Confirmation",
      "from_email": "noreply@yourdomain.com",
      "from_name": "Your Store"
    }
  }'

Node.js

const response = await fetch("https://api.unione.io/en/transactional/api/v1/email/send.json?platform=openclaw", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "X-API-KEY": process.env.UNIONE_API_KEY
  },
  body: JSON.stringify({
    idempotency_key: crypto.randomUUID(),
    message: {
      recipients: [{ email: "recipient@example.com", substitutions: { to_name: "John" } }],
      body: {
        html: "<h1>Hello, {{to_name}}!</h1><p>Your order has been confirmed.</p>",
        plaintext: "Hello, {{to_name}}! Your order has been confirmed."
      },
      subject: "Order Confirmation",
      from_email: "noreply@yourdomain.com",
      from_name: "Your Store"
    }
  })
});
const data = await response.json();
// data.status === "success" → data.job_id, data.emails

Python

import requests, uuid, os

response = requests.post(
    "https://api.unione.io/en/transactional/api/v1/email/send.json?platform=openclaw",
    headers={
        "Content-Type": "application/json",
        "X-API-KEY": os.environ["UNIONE_API_KEY"]
    },
    json={
        "idempotency_key": str(uuid.uuid4()),
        "message": {
            "recipients": [{"email": "recipient@example.com", "substitutions": {"to_name": "John"}}],
            "body": {
                "html": "<h1>Hello, {{to_name}}!</h1><p>Your order has been confirmed.</p>",
                "plaintext": "Hello, {{to_name}}! Your order has been confirmed."
            },
            "subject": "Order Confirmation",
            "from_email": "noreply@yourdomain.com",
            "from_name": "Your Store"
        }
    }
)
data = response.json()  # data["status"] == "success" → data["job_id"], data["emails"]

Go

package main

import (
    "bytes"
    "encoding/json"
    "fmt"
    "net/http"
    "os"
    "github.com/google/uuid"
)

func sendEmail() error {
    payload := map[string]interface{}{
        "idempotency_key": uuid.New().String(),
        "message": map[string]interface{}{
            "recipients": []map[string]interface{}{
                {"email": "recipient@example.com", "substitutions": map[string]string{"to_name": "John"}},
            },
            "body": map[string]string{
                "html":      "<h1>Hello, {{to_name}}!</h1><p>Your order has been confirmed.</p>",
                "plaintext": "Hello, {{to_name}}! Your order has been confirmed.",
            },
            "subject":    "Order Confirmation",
            "from_email": "noreply@yourdomain.com",
            "from_name":  "Your Store",
        },
    }
    body, _ := json.Marshal(payload)
    req, _ := http.NewRequest("POST",
        "https://api.unione.io/en/transactional/api/v1/email/send.json?platform=openclaw",
        bytes.NewReader(body))
    req.Header.Set("Content-Type", "application/json")
    req.Header.Set("X-API-KEY", os.Getenv("UNIONE_API_KEY"))
    resp, err := http.DefaultClient.Do(req)
    if err != nil {
        return err
    }
    defer resp.Body.Close()
    var result map[string]interface{}
    json.NewDecoder(resp.Body).Decode(&result)
    fmt.Println(result) // result["status"] == "success"
    return nil
}

PHP

$ch = curl_init("https://api.unione.io/en/transactional/api/v1/email/send.json?platform=openclaw");
curl_setopt_array($ch, [
    CURLOPT_POST => true,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => [
        "Content-Type: application/json",
        "X-API-KEY: " . getenv("UNIONE_API_KEY")
    ],
    CURLOPT_POSTFIELDS => json_encode([
        "idempotency_key" => bin2hex(random_bytes(16)),
        "message" => [
            "recipients" => [["email" => "recipient@example.com", "substitutions" => ["to_name" => "John"]]],
            "body" => [
                "html" => "<h1>Hello, {{to_name}}!</h1><p>Your order has been confirmed.</p>",
                "plaintext" => "Hello, {{to_name}}! Your order has been confirmed."
            ],
            "subject" => "Order Confirmation",
            "from_email" => "noreply@yourdomain.com",
            "from_name" => "Your Store"
        ]
    ])
]);
$response = curl_exec($ch);
$data = json_decode($response, true); // $data["status"] === "success"

Success response:

{
  "status": "success",
  "job_id": "1ZymBc-00041N-9X",
  "emails": ["recipient@example.com"]
}

Full parameters for message object:

Parameter	Type	Required	Description
recipients	array	Yes	Array of recipient objects. Each has email (required), substitutions (object), metadata (object)
body.html	string	Yes*	HTML content. Use {{variable}} for substitutions
body.plaintext	string	No	Plain text version
subject	string	Yes*	Email subject line. Supports {{substitutions}}
from_email	string	Yes*	Sender email (must be from a verified domain)
from_name	string	No	Sender display name
reply_to	string	No	Reply-to email address
template_id	string	No	Use a stored template instead of body/subject
tags	array	No	Tags for categorizing and filtering
track_links	0/1	No	Enable click tracking (default: 0)
track_read	0/1	No	Enable open tracking (default: 0)
global_language	string	No	Language for unsubscribe footer: en, de, fr, es, it, pl, pt, ru, ua, be
template_engine	string	No	"simple" (default) or "velocity" or "liquid"
global_substitutions	object	No	Variables available to all recipients
attachments	array	No	Array of {type, name, content} where content is base64
skip_unsubscribe	0/1	No	Skip unsubscribe footer (use 1 only for transactional)
headers	object	No	Custom email headers

*Not required if template_id is used.

Top-level parameter:

Parameter	Type	Required	Description
idempotency_key	string	Recommended	Unique key (UUID) to prevent duplicate sends on retry. Max 36 chars.

Send with template:

curl -X POST "https://api.unione.io/en/transactional/api/v1/email/send.json?platform=openclaw" \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $UNIONE_API_KEY" \
  -d '{
    "idempotency_key": "unique-uuid-here",
    "message": {
      "recipients": [
        {
          "email": "customer@example.com",
          "substitutions": {
            "to_name": "Alice",
            "order_id": "ORD-12345",
            "total": "$59.99"
          }
        }
      ],
      "template_id": "your-template-id",
      "from_email": "shop@yourdomain.com",
      "from_name": "My Shop"
    }
  }'

Send to multiple recipients with personalization:

curl -X POST "https://api.unione.io/en/transactional/api/v1/email/send.json?platform=openclaw" \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $UNIONE_API_KEY" \
  -d '{
    "idempotency_key": "unique-uuid-here",
    "message": {
      "recipients": [
        {"email": "alice@example.com", "substitutions": {"to_name": "Alice"}},
        {"email": "bob@example.com", "substitutions": {"to_name": "Bob"}}
      ],
      "body": {
        "html": "<p>Hi {{to_name}}, check out our new {{promo_name}}!</p>"
      },
      "subject": "Special offer for you, {{to_name}}!",
      "from_email": "marketing@yourdomain.com",
      "from_name": "Marketing Team",
      "global_substitutions": {"promo_name": "Summer Sale"},
      "track_links": 1,
      "track_read": 1,
      "tags": ["promo", "summer-2026"]
    }
  }'

---

2. Email Validation — email-validation/single.json

Validate an email address to check if it exists and is deliverable.

curl -X POST "https://api.unione.io/en/transactional/api/v1/email-validation/single.json?platform=openclaw" \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $UNIONE_API_KEY" \
  -d '{"email": "user@example.com"}'

Response:

{
  "status": "success",
  "email": "user@example.com",
  "result": "valid",
  "local_part": "user",
  "domain": "example.com",
  "mx_found": true,
  "mx_record": "mail.example.com"
}

Possible result values: "valid", "invalid", "unresolvable", "unknown".

---

3. Template Management

3.1 Create/Update Template — template/set.json

curl -X POST "https://api.unione.io/en/transactional/api/v1/template/set.json?platform=openclaw" \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $UNIONE_API_KEY" \
  -d '{
    "template": {
      "name": "Order Confirmation",
      "subject": "Your order {{order_id}} is confirmed",
      "template_engine": "simple",
      "body": {
        "html": "<h1>Thank you, {{to_name}}!</h1><p>Order {{order_id}} total: {{total}}</p>",
        "plaintext": "Thank you, {{to_name}}! Order {{order_id}} total: {{total}}"
      },
      "from_email": "shop@yourdomain.com",
      "from_name": "My Shop"
    }
  }'

Response: {"status": "success", "template": {"id": "generated-template-id"}}

To update an existing template, include the "id" field in the template object.

3.2 Get Template — template/get.json

curl -X POST "https://api.unione.io/en/transactional/api/v1/template/get.json?platform=openclaw" \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $UNIONE_API_KEY" \
  -d '{"id": "template-id-here"}'

3.3 List Templates — template/list.json

curl -X POST "https://api.unione.io/en/transactional/api/v1/template/list.json?platform=openclaw" \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $UNIONE_API_KEY" \
  -d '{"limit": 50, "offset": 0}'

3.4 Delete Template — template/delete.json

curl -X POST "https://api.unione.io/en/transactional/api/v1/template/delete.json?platform=openclaw" \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $UNIONE_API_KEY" \
  -d '{"id": "template-id-here"}'

---

4. Webhook Management

Webhooks send real-time notifications about email events to your URL.

4.1 Set Webhook — webhook/set.json

curl -X POST "https://api.unione.io/en/transactional/api/v1/webhook/set.json?platform=openclaw" \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $UNIONE_API_KEY" \
  -d '{
    "url": "https://yourapp.com/unione-webhook",
    "events": {
      "email_status": [
        "delivered", "opened", "clicked", "unsubscribed",
        "soft_bounced", "hard_bounced", "spam"
      ]
    }
  }'

4.2 List Webhooks — webhook/list.json

curl -X POST "https://api.unione.io/en/transactional/api/v1/webhook/list.json?platform=openclaw" \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $UNIONE_API_KEY" \
  -d '{}'

4.3 Get / Delete Webhook — webhook/get.json / webhook/delete.json

# Get
curl -X POST ".../webhook/get.json?platform=openclaw" -H "X-API-KEY: $UNIONE_API_KEY" \
  -H "Content-Type: application/json" -d '{"url": "https://yourapp.com/unione-webhook"}'

# Delete
curl -X POST ".../webhook/delete.json?platform=openclaw" -H "X-API-KEY: $UNIONE_API_KEY" \
  -H "Content-Type: application/json" -d '{"url": "https://yourapp.com/unione-webhook"}'

---

5. Suppression List Management

5.1 Add — suppression/set.json

curl -X POST "https://api.unione.io/en/transactional/api/v1/suppression/set.json?platform=openclaw" \
  -H "Content-Type: application/json" \
  -H "X-API-KEY: $UNIONE_API_KEY" \
  -d '{"email": "user@example.com", "cause": "unsubscribed", "created": "2026-01-15 12:00:00"}'

Cause values: "unsubscribed", "temporary_unavailable", "permanent_unavailable", "complained".

5.2 Check — suppression/get.json

curl -X POST ".../suppression/get.json?platform=openclaw" -H "X-API-KEY: $UNIONE_API_KEY" \
  -H "Content-Type: application/json" -d '{"email": "user@example.com"}'

5.3 List — suppression/list.json

curl -X POST ".../suppression/list.json?platform=openclaw" -H "X-API-KEY: $UNIONE_API_KEY" \
  -H "Content-Type: application/json" -d '{"cause": "hard_bounced", "limit": 50, "offset": 0}'

5.4 Delete — suppression/delete.json

curl -X POST ".../suppression/delete.json?platform=openclaw" -H "X-API-KEY: $UNIONE_API_KEY" \
  -H "Content-Type: application/json" -d '{"email": "user@example.com"}'

---

6. Event Dumps

6.1 Create — event-dump/create.json

curl -X POST ".../event-dump/create.json?platform=openclaw" -H "X-API-KEY: $UNIONE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"start_time": "2026-01-01 00:00:00", "end_time": "2026-01-31 23:59:59", "limit": 50000, "all_events": true}'

6.2 Get / List / Delete

# Get dump status and download URL
curl -X POST ".../event-dump/get.json?platform=openclaw" -H "X-API-KEY: $UNIONE_API_KEY" \
  -H "Content-Type: application/json" -d '{"dump_id": "dump-id"}'

# List all dumps
curl -X POST ".../event-dump/list.json?platform=openclaw" -H "X-API-KEY: $UNIONE_API_KEY" \
  -H "Content-Type: application/json" -d '{}'

# Delete a dump
curl -X POST ".../event-dump/delete.json?platform=openclaw" -H "X-API-KEY: $UNIONE_API_KEY" \
  -H "Content-Type: application/json" -d '{"dump_id": "dump-id"}'

---

7. Tags — tag/list.json / tag/delete.json

# List tags
curl -X POST ".../tag/list.json?platform=openclaw" -H "X-API-KEY: $UNIONE_API_KEY" \
  -H "Content-Type: application/json" -d '{}'

# Delete tag
curl -X POST ".../tag/delete.json?platform=openclaw" -H "X-API-KEY: $UNIONE_API_KEY" \
  -H "Content-Type: application/json" -d '{"tag_id": 123}'

---

8. Projects — project/create.json / project/list.json

# Create project
curl -X POST ".../project/create.json?platform=openclaw" -H "X-API-KEY: $UNIONE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"project": {"name": "My Project", "send_enabled": true}}'

# List projects
curl -X POST ".../project/list.json?platform=openclaw" -H "X-API-KEY: $UNIONE_API_KEY" \
  -H "Content-Type: application/json" -d '{}'

---

9. System Info — system/info.json

curl -X POST ".../system/info.json?platform=openclaw" -H "X-API-KEY: $UNIONE_API_KEY" \
  -H "Content-Type: application/json" -d '{}'

---

10. Subscribe (Double Opt-In) — email/subscribe.json

curl -X POST ".../email/subscribe.json?platform=openclaw" -H "X-API-KEY: $UNIONE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"from_email": "newsletter@yourdomain.com", "from_name": "Newsletter", "to_email": "newsubscriber@example.com"}'

---

Instructions for the Agent

1. Domain setup is mandatory. Before the first send, always check if the user's domain is verified. Run domain/list.json to check. If not verified, guide them through the domain setup process (Section: Domain Setup).
2. Always use api.unione.io as the API host for all requests.
3. Never send an email without explicit user confirmation. Always show the recipient, subject, and body summary before executing email/send.json. Wait for the user to approve. This applies to every send — including test emails and retries with new content.
4. Never modify or delete templates, webhooks, or suppressions without explicit user confirmation. Show what will be changed and wait for approval.
5. Always include idempotency_key in email/send.json requests. Generate a UUID for each unique send. Reuse the same key when retrying.
6. Implement retry logic for 429 and 5xx errors with exponential backoff (see Error Handling section). Never retry 400, 401, 403, 404, 413 errors.
7. For template operations, list available templates first before asking which one to use.
8. For validation, report the result clearly and suggest action.
9. Handle errors gracefully. If a request returns an error, explain what went wrong and suggest a fix.
10. Remind users that the from_email domain must be verified in their UniOne account.
11. Substitution syntax uses double curly braces: {{variable_name}}.
12. Attachments must be base64-encoded. Help the user encode files if needed.
13. Security: Never log or display the full API key. Remind users to keep their API key secret. Recommend using a least-privilege API key scoped to only the required actions.
14. DNS safety: When guiding users through domain DNS setup, instruct them to add records at their DNS provider themselves. Never ask users to paste private keys, certificates, or unrelated secrets into the conversation.
15. Code language: When the user's project uses a specific language (Node.js, Python, Go, PHP, etc.), provide code examples in that language. The examples in this skill can be adapted to any language that can make HTTP POST requests with JSON.
16. Scope: Only interact with UniOne API endpoints documented in this skill. Do not read unrelated files, environment variables, or access third-party services.

Common Workflows

"Send a test email"

1. Check domain verification (domain/list.json)
2. If domain not verified, guide through domain setup
3. Ask for recipient email address
4. Compose a simple test message
5. Confirm with user before sending
6. Execute email/send.json with idempotency_key
7. Report the job_id on success

"Check my deliverability setup"

1. Run system/info.json to get account status
2. Run domain/list.json to check domain verification
3. For each unverified domain, run domain/get-dns-records.json and show required records
4. Run domain/validate-dkim.json to check DKIM
5. Suggest fixes if domains are not fully verified

"Validate a list of emails"

1. For each email, call email-validation/single.json
2. Categorize results: valid, invalid, unknown
3. Report summary

"Set up delivery tracking"

1. Ask for webhook URL and events to track
2. Execute webhook/set.json
3. Confirm setup

Resources

• Full API Reference: https://docs.unione.io/en/web-api-ref
• Getting Started: https://docs.unione.io/en/
• Template Engines: https://docs.unione.io/en/web-api#section-template-engines
• Sign Up: https://cp.unione.io/en/user/registration/