Question 1

What is the Inbox OSS email template builder?

Accepted Answer

The email template builder is the design and authoring environment for every message you send through the platform — transactional and marketing alike. It has two surfaces: a **drag-and-drop visual builder** for non-technical users with starter blocks, brand-kit inheritance, undo history, and mobile preview; and an **MJML editor with syntax highlighting and lint-on-save** for power users who want pixel control. Templates render server-side at send time using Handlebars personalization, so per-recipient substitutions, conditional content blocks, and locale routing are evaluated against each subscriber individually. The same template library serves transactional sends (receipts, password resets), marketing campaigns (newsletters, promotions), and automation flows (drip sequences, win-back) — one source of truth across the entire email program.

Question 2

What is MJML and why does the editor support it?

Accepted Answer

MJML (Mailjet Markup Language) is a markup language designed specifically for **responsive email**. Email HTML is notoriously hard to write because mailbox clients render with inconsistent CSS support — Outlook desktop uses Microsoft Word's HTML renderer, Gmail strips many style attributes, Apple Mail and webmail clients vary in flexbox support. MJML abstracts these inconsistencies: you write semantic components (, , ) and the compiler produces table-based HTML that renders correctly across 50+ email clients. The Inbox OSS MJML editor compiles your source on save and shows a live preview alongside the source. **This is structurally better than competitors like SendGrid Design Library** that produce HTML directly without an intermediate language — you get the same client compatibility with much cleaner authoring.

Question 3

How does Handlebars personalization work in templates?

Accepted Answer

Templates support **full Handlebars syntax** including {{variable}} substitution, {{#if condition}}...{{/if}} conditionals, {{#each array}}...{{/each}} loops, partials for shared components, and custom helpers for date formatting, currency conversion, and string manipulation. Per-recipient data passes through the dynamic_template_data field on /api/v1/mail/send personalizations. **This is the SendGrid-compatible Handlebars dialect** — templates migrated from SendGrid render identically without any syntax change. For more advanced templating needs, the editor also supports Liquid (Shopify's template language) on an opt-in basis, useful for migrations from Klaviyo or any platform that standardized on Liquid.

Question 4

How does this compare to React Email?

Accepted Answer

React Email is a relatively new option where you author email as React components and render to HTML at build time. It is a good developer-experience win for engineering-heavy teams that want to keep email in the same codebase as their app — but it has structural limitations: **templates are baked into your application code**, so non-technical users cannot author or edit them, A/B testing requires deploying both variants, and localization requires shipping per-locale builds. The Inbox OSS template builder produces equivalent (often better) responsive HTML via MJML while keeping templates **editable by non-engineers in the dashboard**, with versioning, audit history, A/B testing, and localization built into the platform. The two approaches can coexist — many customers use React Email for one-off transactional templates and the dashboard builder for marketing.

Question 5

What kind of starter templates are included?

Accepted Answer

The starter library includes 50+ production-ready templates across the standard transactional and marketing categories: **password reset, welcome email, email verification, magic link, two-factor code, order confirmation, shipping notification, abandoned cart, receipt, invoice, subscription renewal, trial expiry warning, plan upgrade, plan downgrade, account suspension notice, security alert, newsletter, product announcement, blog digest, event invitation, survey request, NPS prompt, referral request, re-engagement, win-back, and many more**. Each is fully responsive, MJML-source-included, brand-kit-aware, and accessibility-tested. Templates are starting points — duplicate any one to your account and customize the copy, layout, and styling to fit your brand.

Question 6

How does per-recipient localization work?

Accepted Answer

Pass a **locale** key in the dynamic_template_data field (e.g., locale: "fr-FR" or "ja-JP") on each personalization, and the rendering engine routes to the matching localized template version automatically. Each template can have any number of locale variants (the parent template is the default; per-locale overrides apply substitution-style). RTL (Arabic, Hebrew) and CJK (Chinese, Japanese, Korean) rendering is handled correctly — the engine sets the appropriate dir attribute, picks fallback fonts that render the script, and aligns text per the locale convention. Currency, date, and number formatting are auto-localized by passing currency-amount and date-value through built-in helpers ({{formatCurrency price locale}}, {{formatDate timestamp locale}}).

Question 7

Can I share assets and brand styles across templates?

Accepted Answer

Yes. The **brand kit** is an account-level configuration where you pin colors, fonts, button styles, header/footer components, and logos once. Every new template inherits the brand kit so all your email stays visually consistent without copy-paste. The **asset library** stores uploaded images on our CDN with auto-compression and serves them at the optimal format (WebP for clients that support it, PNG/JPG fallback) — upload once, reuse across every template. Partials (reusable template fragments) live at the account level and can be included in any template via {{> partial-name}}. For multi-brand or agency accounts, brand kits scope per-domain or per-team so each brand keeps its own visual identity.

Question 8

Does the editor preview emails across different mailbox clients?

Accepted Answer

Yes. The editor includes a **live preview panel** showing how your template renders in Gmail web, Gmail iOS/Android, Apple Mail, Outlook desktop (Windows and Mac), Outlook web, Yahoo Mail, and a generic mobile rendering. The previews are generated via headless rendering against actual client engines — not best-guess CSS approximations. For deeper compatibility testing, the optional Litmus or Email on Acid integration runs your template against 90+ real client environments and surfaces a visual diff. Both integrations are available on Pro and above; the built-in 6-client preview is included on every plan.

Question 9

How do I version and audit changes to templates?

Accepted Answer

Every save creates a **snapshot** captured with the editor identity, timestamp, and a diff of what changed. The dashboard exposes the version history for any template with one-click revert to any previous snapshot — useful when an over-eager edit breaks rendering or when you need to roll back a template change that caused a metrics regression. For high-stakes templates (transactional flows that send to every signup), the dashboard supports a **review-required workflow** where changes go to draft and require a second reviewer to publish. The audit log is exportable as JSON for SOC 2 and ISO 27001 evidence requirements.

Question 10

How does template testing fit into a CI/CD workflow?

Accepted Answer

The platform exposes a **sandbox mode** on /api/v1/mail/send that fully validates a send (auth, schema, template rendering, suppression check) without delivering — perfect for CI smoke tests that verify your application is producing well-formed sends. For deeper template testing, the /api/v1/templates/{id}/preview endpoint accepts dynamic_template_data and returns the rendered HTML and text bodies, which you can snapshot-test against expected output. Combined with our published OpenAPI specification and JSON Schema for events, the entire template-to-send-to-event pipeline is testable end-to-end without sending real emails or consuming credits.

Design once. Render perfectly. Everywhere.

Visual builder

Code editor

Asset library

Brand kit

Per-recipient locale

Starter library

Frequently asked questions about email templates

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