Version 0.30.0 Jun 24, 2026

Transactional Emails

You can now send one-off transactional emails, such as order confirmations, password resets, and magic links, with the Keila API.

Transactional emails are sent to one recipient at a time, usually in response to an action the user has just taken. Typical use-cases for transactional emails include sending order confirmations or password reset links. You can now use the Keila API to send such messages; either to an existing contact or to a recipient that is not currently in your contact list.

Sending a Message

Transactional messages can currently only be sent via the API:

POST /api/v1/messages

{
  "data": {
    "type": "text",
    "sender_id": "ms_12345",
    "recipient_email": "jane@example.com",
    "subject": "Your order is confirmed",
    "text_body": "Hi {{ contact.first_name }}, thanks for your order."
  }
}

In order to send a transactional email, you need to specify the recipient, the email content and subject, and a sender.

Choosing the Recipient

You specify the message recipient in one of three ways:

• recipient_email – a plain email address.
• contact_id – the ID of a contact in Keila.
• external_contact_id – an ID from your own system, stored in the external_id property of the contact.

When the address specified via recipient_email matches a contact in your project, Keila automatically links the message to that contact. This makes the contact’s details available to your template.

Specifying Message Content

The email body can be provided directly or you can use a template. To provide the message content directly, you need to specify the email type (mjml, html, or text) alongside the corresponding body field (mjml_body, html_body, text_body). In this case, you also must specify the subject field.

If you specify a template via template_id, you still need to specify the email type. But you may now specify content slots instead (mjml_content, html_content, or text_content). If you don’t specify a subject, the template name will be used as the subject.

Additional variables can be given as assigns:

{
  "data": {
    "type": "html",
    "sender_id": "ms_12345",
    "template_id": "tpl_12345",
    "recipient_email": "jane@example.com",
    "subject": "Your magic link",
    "assigns": { "magic_link": "https://example.com/login?token=..." }
  }
}

CC and BCC

To copy other people on the message, add cc or bcc. Each one takes either a single address list as a string or an array of separate addresses:

"cc": "Jane <jane@example.com>, john@example.com"

"cc": ["jane@example.com", "john@example.com"]

Preview Before You Send

You can render a preview of the HTML and plain text versions of a transactional email by calling the render action endpoint.

POST /api/v1/messages/actions/render

This returns the rendered subject, html_body, and text_body without actually sending an email.

Read the full API reference in the Transactional Messages API docs.