Email templates

An email message definition lets non-developers own the subject and body. Your application sends by key and supplies variables; the definition renders the rest. Email and SMS share one authoring model — the channel is chosen when the definition is created and is fixed for its lifetime.

What an email definition carries

• from — the sender identity, authored on the definition. In sandbox an absent from falls back to a synthetic sandbox address; live sending requires a verified domain.
• Subject, text, and HTML — with variables interpolated from the data you send.
• Per-locale variants — override the subject or body for a locale; the base content fills any gap.

Variables and escaping

Variables use the same stable-key grammar as SMS. In the HTML body, variable values are HTML-escaped so a value containing < or & cannot inject markup. The subject rejects carriage returns and line feeds, closing the header-injection vector. You never need to pre-escape values yourself.

Preview shows the rendered result and its cost

const preview = await fabric.messages.preview("receipt.paid", {
  channel: "email",
  data: { name: "Ama", amount: "GHS 120.00" },
  to: "ama@example.com",
});

const email = preview.data.emailPreview; // null unless the definition is an email channel
console.log(email?.subject, email?.sizeBytes, email?.costMinor);

Email is priced flat per send (not by size or segments). A message over the hard size ceiling is refused before it is priced — a blocker, not a silent truncation. Preview and send render byte-for-byte identically, so the previewed cost is the cost you pay.

Send by key

await fabric.messages.send("receipt.paid", {
  to: "ama@example.com",
  data: { name: "Ama", amount: "GHS 120.00" },
  idempotencyKey: "receipt:GH-4821",
});

The definition’s channel makes to an email address; a phone number is refused before acceptance. Use direct email instead when your server already owns the subject and body.