Template Guide

Optail templates use MJML for responsive email markup and Handlebars for variable interpolation. Templates are versioned — you can preview with sample data, publish new versions, and roll back to any previous version.

Creating a Template

1. Create the template container

curl -X POST https://api.optail.io/v1/templates \
  -H "Authorization: Bearer ms_live_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Welcome Email",
    "description": "Sent when a new user signs up",
    "tags": ["onboarding"]
  }'

This creates a template with no versions yet. Note the id from the response.

2. Create the first version with MJML

curl -X POST https://api.optail.io/v1/templates/TPL_ID/versions \
  -H "Authorization: Bearer ms_live_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "mjmlSource": "<mjml><mj-body><mj-section><mj-column><mj-text>Hello {{name}}!</mj-text><mj-button href=\"{{activationUrl}}\">Activate Account</mj-button></mj-column></mj-section></mj-body></mjml>",
    "htmlContent": "<html><body><h1>Hello {{name}}!</h1><a href=\"{{activationUrl}}\">Activate Account</a></body></html>",
    "textContent": "Hello {{name}}! Activate your account: {{activationUrl}}",
    "variablesSchema": {
      "name": "string",
      "activationUrl": "string"
    }
  }'

If you provide mjmlSource, Optail compiles it to HTML server-side. The htmlContent field serves as a fallback if MJML compilation has issues.

3. Preview with sample data

curl -X POST https://api.optail.io/v1/templates/TPL_ID/preview \
  -H "Authorization: Bearer ms_live_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "variables": {
      "name": "Jane",
      "activationUrl": "https://app.example.com/activate?token=abc"
    }
  }'

The response contains the rendered HTML with variables replaced.

MJML Basics

MJML is a markup language that compiles to responsive HTML email. It handles the complex table-based layouts and inline styles that email clients require.

<mjml>
  <mj-body>
    <mj-section>
      <mj-column>
        <mj-image src="https://yourdomain.com/logo.png" width="150px" />
        <mj-text font-size="20px" font-weight="bold">
          Welcome, {{name}}!
        </mj-text>
        <mj-text>
          Thanks for signing up. Click below to activate your account.
        </mj-text>
        <mj-button href="{{activationUrl}}" background-color="#4F46E5">
          Activate Account
        </mj-button>
      </mj-column>
    </mj-section>
  </mj-body>
</mjml>

Key MJML components:

Component	Description
`<mj-body>`	Root email body.
`<mj-section>`	A horizontal row (like a table row).
`<mj-column>`	A column within a section.
`<mj-text>`	Text block with styling.
`<mj-image>`	Responsive image.
`<mj-button>`	Call-to-action button.
`<mj-divider>`	Horizontal line separator.
`<mj-spacer>`	Vertical spacing.

Handlebars Variables

Use {{ variableName }} syntax in your templates. Variables are replaced at send time with the values passed in the variables field.

<mj-text>Hello {{firstName}} {{lastName}}!</mj-text>
<mj-text>Your order #{{orderNumber}} has shipped.</mj-text>
<mj-button href="{{trackingUrl}}">Track Package</mj-button>

When sending:

await optail.send({
  to: 'user@example.com',
  from: 'orders@yourdomain.com',
  subject: 'Your order #{{orderNumber}} has shipped',
  templateId: 'tpl-uuid',
  variables: {
    firstName: 'Jane',
    lastName: 'Doe',
    orderNumber: '12345',
    trackingUrl: 'https://tracking.example.com/12345',
  },
});

Variables in the subject field are also replaced.

Versioning and Rollback

Every time you create a new version, it becomes the current (active) version. Previous versions are preserved.

List versions

curl https://api.optail.io/v1/templates/TPL_ID/versions \
  -H "Authorization: Bearer ms_live_your_api_key"

Roll back to a previous version

curl -X POST https://api.optail.io/v1/templates/TPL_ID/rollback/VERSION_ID \
  -H "Authorization: Bearer ms_live_your_api_key"

This sets the specified version as the current version without deleting newer versions. You can roll forward again at any time.

Preview a specific version

curl -X POST https://api.optail.io/v1/templates/TPL_ID/preview \
  -H "Authorization: Bearer ms_live_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "versionId": "VERSION_ID",
    "variables": { "name": "Jane" }
  }'