Introduction
Emailens is an email QA tool that previews how HTML emails render across 13 email clients including Gmail, Outlook, Apple Mail, Yahoo, HEY Mail, Superhuman, and more.
Emailens tracks 250+ CSS properties across 13 email clients, scores compatibility from 0 to 100, simulates dark mode, checks DNS deliverability, and captures screenshots — all in one API call.
How it works
- Submit your HTML email (or React Email JSX, MJML, or Maizzle)
- Transform — Emailens rewrites CSS for each of 13 email clients
- Analyze — CSS compatibility warnings with framework-aware fix snippets
- Score — 0-100 compatibility score per client
- Dark mode — simulated dark mode variants
- Screenshots — rendered previews via headless browser
Use it your way
- Web app — paste HTML into the preview tool at emailens.dev
- REST API —
POST /api/previewwith your HTML - MCP server — use with Claude Desktop or Claude Code
- GitHub Action — fail PRs when email compatibility drops
- Engine package —
@emailens/engineas a standalone npm package
Supported email clients
| Client | ID | Category | Engine | Dark mode |
|---|---|---|---|---|
| Gmail | gmail-web | Webmail | Gmail Web | Yes |
| Gmail Android | gmail-android | Mobile | Gmail Mobile | Yes |
| Gmail iOS | gmail-ios | Mobile | Gmail Mobile | Yes |
| Outlook 365 | outlook-web | Webmail | Outlook Web | Yes |
| Outlook (New) | outlook-windows | Desktop | Outlook Web | Yes |
| Outlook Classic | outlook-windows-legacy | Desktop | Microsoft Word | Yes |
| Apple Mail | apple-mail-macos | Desktop | WebKit | Yes |
| Apple Mail iOS | apple-mail-ios | Mobile | WebKit | Yes |
| Yahoo Mail | yahoo-mail | Webmail | Yahoo | Yes |
| Samsung Mail | samsung-mail | Mobile | Samsung | Yes |
| Thunderbird | thunderbird | Desktop | Gecko | No |
| HEY Mail | hey-mail | Webmail | WebKit | Yes |
| Superhuman | superhuman | Desktop | Blink | Yes |
Next steps
- Quick start — get a preview in under a minute
- API reference — integrate via REST
- Engine package — use the core library directly