Send Email Messages

Send transactional and marketing emails to any recipient using YeboLink's email API — powered by Resend, with no SMTP setup required.

Endpoint

POST /api/v1/messages/send

Authentication

Requires API Key authentication via X-API-Key header.

Request Body

Parameter	Type	Required	Description
`to`	string	Yes	Recipient email address (must be valid email format)
`channel`	string	Yes	Must be `"email"`
`content`	object	Yes	Message content object
`content.subject`	string	Yes	Email subject line (required for email channel)
`content.html`	string	Recommended	HTML body of the email
`content.text`	string	No	Plain text fallback. If omitted and `html` is provided, recipients see HTML.
`content.reply_to`	string	No	Email address recipient replies are routed to (must be a valid email format). Defaults to your workspace's account email if omitted.
`from`	string	No	Sender display name shown in inbox (e.g. `"KESHLESS"`, `"MyApp"`). Defaults to your workspace sender name.
`scheduled_at`	string	No	ISO 8601 timestamp to send later instead of immediately — see Scheduling
`metadata`	object	No	Custom key-value pairs for your own tracking

The Idempotency-Key header is supported here too, making a retried email send safe from duplicates — see Idempotency.

Required Fields

For email channel: content.subject is required. At least one of content.html or content.text must be provided.

Sender Name

The from field sets the display name only. Emails always send from <name>@mail.yebolink.com. Contact support to use a custom domain.

Reply-To

Every email sends from the shared mail.yebolink.com address, so a recipient's "Reply" always needs somewhere real to land. Set content.reply_to to route replies to your own inbox — if you leave it out, YeboLink falls back to your workspace's account email so replies are never lost.

Try It Now

Send Email

API Key (required to test):

Your API key is stored locally and never sent to our servers. Get an API key →

Example Request

bash

curl -X POST https://api.yebolink.com/api/v1/messages/send \
  -H "Content-Type: application/json" \
  -H "X-API-Key: ybk_your_api_key" \
  -d '{
    "to": "user@example.com",
    "channel": "email",
    "content": {
      "subject": "Your order is confirmed",
      "html": "<h1>Order Confirmed ✓</h1><p>Thanks for your purchase. Your order #12345 is on its way.</p>",
      "reply_to": "support@yourcompany.com"
    },
    "metadata": {
      "user_id": "12345",
      "order_id": "ORD-12345"
    }
  }'

javascript

const sendEmail = async (to, subject, html, metadata = {}) => {
  const response = await fetch('https://api.yebolink.com/api/v1/messages/send', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      'X-API-Key': process.env.YEBOLINK_API_KEY
    },
    body: JSON.stringify({
      to,
      channel: 'email',
      content: { subject, html },
      metadata
    })
  });

  if (!response.ok) {
    const error = await response.json();
    throw new Error(error.message);
  }

  return await response.json();
};

// Usage
const result = await sendEmail(
  'user@example.com',
  'Your order is confirmed',
  '<h1>Order Confirmed ✓</h1><p>Your order #12345 is on its way.</p>',
  { order_id: 'ORD-12345' }
);

console.log('Message sent:', result.data.message_id);
console.log('Credits used:', result.data.credits_used);

python

import os
import requests

def send_email(to: str, subject: str, html: str, metadata: dict = None):
    response = requests.post(
        'https://api.yebolink.com/api/v1/messages/send',
        headers={'X-API-Key': os.environ.get('YEBOLINK_API_KEY')},
        json={
            'to': to,
            'channel': 'email',
            'content': {'subject': subject, 'html': html},
            'metadata': metadata or {}
        }
    )
    response.raise_for_status()
    return response.json()

result = send_email(
    to='user@example.com',
    subject='Your order is confirmed',
    html='<h1>Order Confirmed ✓</h1><p>Your order #12345 is on its way.</p>',
    metadata={'order_id': 'ORD-12345'}
)

print(f"Message sent: {result['data']['message_id']}")
print(f"Credits used: {result['data']['credits_used']}")

php

<?php

function sendEmail($to, $subject, $html, $metadata = []) {
    $curl = curl_init();
    curl_setopt_array($curl, [
        CURLOPT_URL => 'https://api.yebolink.com/api/v1/messages/send',
        CURLOPT_RETURNTRANSFER => true,
        CURLOPT_POST => true,
        CURLOPT_HTTPHEADER => [
            'Content-Type: application/json',
            'X-API-Key: ' . getenv('YEBOLINK_API_KEY')
        ],
        CURLOPT_POSTFIELDS => json_encode([
            'to' => $to,
            'channel' => 'email',
            'content' => ['subject' => $subject, 'html' => $html],
            'metadata' => $metadata
        ])
    ]);

    $response = curl_exec($curl);
    $httpCode = curl_getinfo($curl, CURLINFO_HTTP_CODE);
    curl_close($curl);

    if ($httpCode !== 201) {
        $error = json_decode($response, true);
        throw new Exception($error['message']);
    }

    return json_decode($response, true);
}

$result = sendEmail(
    'user@example.com',
    'Your order is confirmed',
    '<h1>Order Confirmed ✓</h1><p>Your order #12345 is on its way.</p>',
    ['order_id' => 'ORD-12345']
);

echo "Message sent: " . $result['data']['message_id'] . "\n";
echo "Credits used: " . $result['data']['credits_used'] . "\n";
?>

package main

import (
    "bytes"
    "encoding/json"
    "fmt"
    "io"
    "net/http"
    "os"
)

type EmailRequest struct {
    To       string                 `json:"to"`
    Channel  string                 `json:"channel"`
    Content  map[string]string      `json:"content"`
    Metadata map[string]string      `json:"metadata,omitempty"`
}

func sendEmail(to, subject, html string, metadata map[string]string) (map[string]interface{}, error) {
    payload := EmailRequest{
        To:      to,
        Channel: "email",
        Content: map[string]string{
            "subject": subject,
            "html":    html,
        },
        Metadata: metadata,
    }

    jsonPayload, _ := json.Marshal(payload)
    req, _ := http.NewRequest("POST", "https://api.yebolink.com/api/v1/messages/send", bytes.NewBuffer(jsonPayload))
    req.Header.Set("Content-Type", "application/json")
    req.Header.Set("X-API-Key", os.Getenv("YEBOLINK_API_KEY"))

    resp, err := http.DefaultClient.Do(req)
    if err != nil {
        return nil, err
    }
    defer resp.Body.Close()

    body, _ := io.ReadAll(resp.Body)
    var result map[string]interface{}
    json.Unmarshal(body, &result)
    return result, nil
}

func main() {
    result, err := sendEmail(
        "user@example.com",
        "Your order is confirmed",
        "<h1>Order Confirmed ✓</h1><p>Your order #12345 is on its way.</p>",
        map[string]string{"order_id": "ORD-12345"},
    )
    if err != nil {
        fmt.Printf("Error: %v\n", err)
        return
    }
    data := result["data"].(map[string]interface{})
    fmt.Printf("Message sent: %s\n", data["message_id"])
    fmt.Printf("Credits used: %v\n", data["credits_used"])
}

Response

Success (201 Created)

json

{
  "success": true,
  "data": {
    "message_id": "550e8400-e29b-41d4-a716-446655440000",
    "status": "queued",
    "credits_used": "0.10",
    "created_at": "2025-11-02T12:00:00Z"
  }
}

Field	Type	Description
`message_id`	string	Unique identifier for the message
`status`	string	Always `queued` on creation
`credits_used`	number	Credits deducted (0.1 per email)
`created_at`	string	ISO 8601 timestamp

Error Responses

Invalid Email Address (400)

json

{
  "success": false,
  "error": "validation_error",
  "message": "Invalid email address format"
}

Insufficient Credits (402)

json

{
  "success": false,
  "error": "insufficient_credits",
  "message": "Not enough credits. You need 0.1 credits but have 0."
}

Invalid API Key (401)

json

{
  "success": false,
  "error": "unauthorized",
  "message": "Invalid or missing API key"
}

Use Cases

Welcome Email

javascript

const sendWelcome = (email, name) => sendEmail(
  email,
  `Welcome to MyApp, ${name}!`,
  `<h1>Welcome, ${name}!</h1>
   <p>Your account is ready. <a href="https://myapp.com/dashboard">Get started →</a></p>`
);

OTP / Verification

javascript

const sendOTP = (email, code) => sendEmail(
  email,
  'Your verification code',
  `<p>Your code is: <strong style="font-size:24px">${code}</strong></p>
   <p>Expires in 10 minutes. Do not share it.</p>`
);

Order Confirmation

javascript

const sendOrderConfirmation = (email, order) => sendEmail(
  email,
  `Order #${order.id} confirmed`,
  `<h2>Order Confirmed ✓</h2>
   <p>Total: $${order.total}</p>
   <p>Estimated delivery: ${order.deliveryDate}</p>
   <a href="https://myapp.com/orders/${order.id}">Track your order →</a>`
);

Invoice / Receipt

javascript

const sendInvoice = (email, invoice) => sendEmail(
  email,
  `Invoice #${invoice.number} from MyApp`,
  `<h2>Invoice #${invoice.number}</h2>
   <p>Amount due: $${invoice.amount}</p>
   <p>Due date: ${invoice.dueDate}</p>
   <a href="${invoice.pdfUrl}">Download PDF</a>`
);

Password Reset

javascript

const sendPasswordReset = (email, resetLink) => sendEmail(
  email,
  'Reset your password',
  `<p>Click below to reset your password. Link expires in 2 hours.</p>
   <a href="${resetLink}" style="background:#6366f1;color:white;padding:12px 24px;border-radius:6px;text-decoration:none">
     Reset Password
   </a>
   <p>If you didn't request this, ignore this email.</p>`
);

Credits & Pricing

Cost: 0.1 credits per email
Delivery: Sent within seconds via Resend
No volume limits beyond your credit balance

See Billing for credit packages and pricing.

Next Steps

Send SMS Messages — Fast notifications, OTPs
Send Bulk Messages — Send to thousands at once
Setup Webhooks — Track delivery events
Channels Overview — Compare all channels

Send Email Messages ​

Endpoint ​

Authentication ​

Request Body ​

Try It Now ​

Send Email

Example Request ​

Response ​

Success (201 Created) ​

Error Responses ​

Invalid Email Address (400) ​

Insufficient Credits (402) ​

Invalid API Key (401) ​

Use Cases ​

Welcome Email ​

OTP / Verification ​

Order Confirmation ​

Invoice / Receipt ​

Password Reset ​

Credits & Pricing ​

Next Steps ​

Send Email Messages

Endpoint

Authentication

Request Body

Try It Now

Example Request

Response

Success (201 Created)

Error Responses

Invalid Email Address (400)

Insufficient Credits (402)

Invalid API Key (401)

Use Cases

Welcome Email

OTP / Verification

Order Confirmation

Invoice / Receipt

Password Reset

Credits & Pricing

Next Steps