[MarkNLD]

Summary

Adds a Transactional Templates guide and updates the homepage and facts page so they cover campaigns as well as transactional email.

New page: /send-api/templates

• When to use a template rather than Create Message, and how it differs from campaign templates
• Creating a template in the dashboard (Simple Editor, Advanced Editor, HTML upload) or with the API
• Variables: required vs fallback, HTML escaping and |safe, reserved email and unsubscribe_url
• Draft, publish and versions (50 kept), with a warning that unpublished changes are not sent
• Sending with Create Template Message (curl example, what a request can and cannot override, up to 100 recipients)
• Permissions, the exact error responses, tracking (template_id on messages, MCP)
• Menu icon file-code, placed after Send email in the Send API group

Homepage (index.mdx)

• Title "Transactional Email, SMTP Relay and Campaigns Docs"; description and intro mention Campaign Builder and the shared 1,000 free emails
• New Quick Start cards: Transactional Templates, Campaigns, Marketing Domains
• Campaign Builder in Built for Developers and in What's Next

Facts (facts.mdx)

• Same intro as the homepage
• "Emails included per month, transactional and campaigns combined"
• Campaign Builder row on all plans, with marketing domains and the daily marketing limit
• Limits: Create Template Message 100 recipients, 1 to 50 lists per campaign, template content 200 KB

Cross-links

• send-email Template Variables accordion, October changelog entry, glossary (new "Transactional template" term)

Checks

• Rebased on current main (includes Docs: October 2026 changelog — changes since the release #30)
• Every claim on the new page checked against the API reference
• All internal links resolve, docs.json parses, no em dashes

For review

• The page says templates are API only (SMTP cannot send one); this is stated nowhere else in the docs yet
• The fallback syntax {{ name|default("...") }} is otherwise only documented on the CLI templates page