Sending Emails

Send emails with attachments, CC/BCC, and custom labels

Overview

Send emails from any inbox with full support for HTML, plain text, attachments, CC/BCC recipients, and custom labels. All sent emails are automatically organized into threads.

Sending a Basic Email

Node.js SDK

import Sendook from "@sendook/node";

const client = new Sendook("your_api_key");

// Send an email
await client.inbox.message.send({
  inboxId: "inbox_123",
  to: ["[e-mail]"],
  subject: "Welcome to Sendook!",
  text: "Thanks for signing up.",
  html: "<p>Thanks for signing up.</p>"
});

curl -X POST https://api.sendook.com/v1/inboxes/inbox_123/messages/send \
  -H "Authorization: Bearer your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "to": ["[e-mail]"],
    "subject": "Welcome to Sendook!",
    "text": "Thanks for signing up.",
    "html": "<p>Thanks for signing up.</p>"
  }'

Both text and html fields are required. The HTML version will be shown to email clients that support it, while the text version is used as a fallback.

Required Parameters

Parameter	Type	Description
inboxId	string	ID of the inbox to send from
to	string[]	Array of recipient email addresses
subject	string	Email subject line
text	string	Plain text version of the email
html	string	HTML version of the email

Optional Parameters

CC and BCC

Send copies to additional recipients:

await client.inbox.message.send({
  inboxId: "inbox_123",
  to: ["[e-mail]"],
  cc: ["[e-mail]", "[e-mail]"],
  bcc: ["[e-mail]"],
  subject: "Project Update",
  text: "Here's the latest update...",
  html: "<p>Here's the latest update...</p>"
});

Labels

Organize emails with custom labels for easier filtering:

await client.inbox.message.send({
  inboxId: "inbox_123",
  to: ["[e-mail]"],
  labels: ["onboarding", "automated", "welcome-series"],
  subject: "Welcome!",
  text: "Welcome to our platform.",
  html: "<p>Welcome to our platform.</p>"
});

Labels are useful for categorizing messages in your dashboard and filtering messages via the API.

Attachments

Include files with your emails:

await client.inbox.message.send({
  inboxId: "inbox_123",
  to: ["[e-mail]"],
  subject: "Invoice #1234",
  text: "Please find your invoice attached.",
  html: "<p>Please find your invoice attached.</p>",
  attachments: [
    {
      content: "base64EncodedContent...",
      name: "invoice.pdf",
      contentType: "application/pdf"
    },
    {
      content: "base64EncodedImageContent...",
      name: "logo.png",
      contentType: "image/png"
    }
  ]
});

Attachment Properties

Property	Type	Required	Description
content	string	Yes	Base64-encoded file content
name	string	No	Filename (e.g., “document.pdf”)
contentType	string	No	MIME type (e.g., “application/pdf”)

Attachment content must be base64-encoded. Most programming languages have built-in libraries to encode files to base64.

Replying to Messages

Reply to an existing message to continue the conversation thread:

Node.js SDK

await client.inbox.message.reply({
  inboxId: "inbox_123",
  messageId: "msg_456",
  text: "Thanks for your message!",
  html: "<p>Thanks for your message!</p>"
});

curl -X POST https://api.sendook.com/v1/inboxes/inbox_123/messages/msg_456/reply \
  -H "Authorization: Bearer your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "text": "Thanks for your message!",
    "html": "<p>Thanks for your message!</p>"
  }'

When you reply:

• The subject is automatically prefixed with “Re:”
• The recipient is set to the sender of the original message
• The reply is added to the same thread as the original message

Response Format

Successful send requests return the created message object:

{
  "id": "msg_789",
  "organizationId": "org_456",
  "inboxId": "inbox_123",
  "threadId": "thread_012",
  "from": "[e-mail]",
  "fromInboxId": "inbox_123",
  "to": ["[e-mail]"],
  "cc": [],
  "bcc": [],
  "labels": ["welcome"],
  "subject": "Welcome to Sendook!",
  "text": "Thanks for signing up.",
  "html": "<p>Thanks for signing up.</p>",
  "attachments": [],
  "status": "sent",
  "externalMessageId": "<aws-ses-message-id>",
  "createdAt": "2024-01-01T12:00:00.000Z",
  "updatedAt": "2024-01-01T12:00:00.000Z"
}

Message Status

Messages go through different statuses:

Status	Description
sent	Message was successfully sent to AWS SES
delivered	Message was delivered to recipient’s mail server
bounced	Message bounced (invalid email or server rejection)
complained	Recipient marked the message as spam
rejected	Message was rejected before sending

You’ll receive webhook events for each status change. See Webhooks for details.

Rate Limits

Sendook implements rate limiting to prevent abuse:

• 100 emails per hour per API key
• Rate limit resets hourly

If you exceed the rate limit, the API will return a 429 error. Plan your email sending accordingly or contact support for higher limits.

Threads

All sent messages are automatically organized into threads:

• New messages create a new thread
• Replies are added to existing threads
• Each thread contains all messages in a conversation

Learn more in Threads.

Webhooks

Sending emails triggers the following webhook events:

• message.sent - Message was sent to AWS SES
• message.delivered - Message was delivered successfully
• message.bounced - Message bounced
• message.complained - Recipient marked as spam
• message.rejected - Message was rejected

See Webhooks for setup instructions.

Best Practices

Always include both text and HTML

Some email clients don’t support HTML or users may have it disabled. Always provide both versions for the best user experience.

Keep attachments reasonable

Large attachments can cause delivery issues. Consider hosting large files and including download links instead.

Use labels for organization

Labels make it easier to filter and search messages later. Use consistent naming conventions for your labels.

Test with BCC

When testing in production, use BCC to send yourself a copy without exposing your email to recipients.

Monitor delivery status

Set up webhooks to track delivery status and handle bounces appropriately in your application.

Next Steps

Receive Emails

Learn how to receive and process incoming emails

Webhooks

Set up webhooks to track message status

Threads

Understand how threads organize conversations

Custom Domains

Improve deliverability with custom domains