This server provides comprehensive tools for analyzing, optimizing, and verifying HTML emails across 15 major email clients — helping you catch compatibility issues before sending.
preview_email: Full compatibility preview including HTML transformation for 15 clients, CSS analysis, per-client scores, dark mode simulation, inbox preview, and email size checks.
analyze_email: Quick CSS compatibility analysis returning per-client scores and warnings.
audit_email: Comprehensive quality audit covering CSS compatibility, spam scoring, link validation, accessibility, images, inbox preview, Gmail clipping, and template variables. Specific checks can be skipped.
fix_email: Generate structured fix instructions in Markdown format for detected compatibility issues, optionally scoped to a specific email client.
diff_emails: Compare two versions of email HTML to identify score changes, resolved issues, and newly introduced issues per client.
list_clients: Retrieve all 15 supported email clients with their IDs, rendering engines, and dark mode support status.
check_deliverability: Analyze a domain's deliverability via SPF, DKIM, DMARC, MX, and BIMI record checks, returning a 0–100 score and actionable issues (no API key required).
capture_screenshots (API key required): Render real browser screenshots across 15 clients in light and/or dark mode, hosted on CDN.
share_preview (API key + Dev plan required): Generate a shareable link to the full email analysis — recipients can view it without an account.
Supported input formats: html, jsx, mjml, maizzle.
Provides compatibility analysis and previews for email clients on the Android platform, including Gmail and Outlook Android.
Analyzes and previews email rendering for Apple Mail across macOS and iOS platforms.
Performs deep CSS compatibility analysis for HTML emails, identifying warnings and scores for 15 different email clients.
Offers comprehensive tools to analyze, preview, and fix email rendering issues specifically for Gmail across web, Android, and iOS.
Supports email compatibility analysis and previewing for the HEY Mail service.
Facilitates email compatibility testing and previewing for mobile clients on iOS, such as Apple Mail, Gmail, and Outlook.
Enables compatibility analysis and previews for Apple Mail on the macOS operating system.
Outputs structured fix instructions and audit results in Markdown format for easy application by AI or developers.
Provides compatibility analysis and rendering previews for Samsung Mail.
Offers email rendering analysis and compatibility previews for the Thunderbird email client.
Email rendering analysis for AI assistants
MCP server for email compatibility analysis. Analyze, preview, diff, and fix HTML emails across 21 email clients — plus capture real screenshots and create shareable links with an optional API key.
Why your assistant needs this: across the 255 CSS and HTML features we track, only 6 are fully supported in every major email client (see the data). Ask Claude to check your email before you send it.
Built on @emailens/engine. Also available as a GitHub Action.
npx -y @emailens/mcpRelated MCP server: polydoc-mcp
Add to claude_desktop_config.json:
{
"mcpServers": {
"emailens": {
"command": "npx",
"args": ["-y", "@emailens/mcp"]
}
}
}claude mcp add emailens -- npx -y @emailens/mcp{
"mcpServers": {
"emailens": {
"command": "npx",
"args": ["-y", "@emailens/mcp"],
"env": {
"EMAILENS_API_KEY": "ek_live_..."
}
}
}
}Get your free API key at emailens.dev/settings/api-keys.
Use the hosted endpoint — no npm or Node.js needed. API key required.
{
"mcpServers": {
"emailens": {
"url": "https://emailens.dev/api/mcp",
"headers": {
"Authorization": "Bearer ek_live_..."
}
}
}
}preview_emailFull email compatibility preview — transforms HTML for 21 clients, analyzes CSS, generates scores, simulates dark mode, checks inbox preview and email size.
Parameter | Type | Required | Description |
| string | Yes | Email HTML source |
| string[] | No | Filter to specific client IDs |
| enum | No |
|
analyze_emailQuick CSS compatibility analysis — returns per-client scores and warnings. Faster than audit_email when you only need CSS compatibility.
Parameter | Type | Required | Description |
| string | Yes | Email HTML source |
| enum | No | Input format |
audit_emailComprehensive quality audit — CSS compatibility, spam scoring, link validation, accessibility, images, inbox preview, size (Gmail clipping), template variables, content overflow, and visual bugs.
Parameter | Type | Required | Description |
| string | Yes | Email HTML source |
| enum | No | Input format |
| string[] | No | Checks to skip (e.g. |
fix_emailGenerate a structured fix prompt for compatibility issues. Returns markdown with fix instructions that the AI can apply directly.
Parameter | Type | Required | Description |
| string | Yes | Email HTML to fix |
| enum | No | Controls fix syntax |
| enum | No |
|
| string | No | Client ID for scoped fixes |
list_clientsList all 21 supported email clients with IDs, names, engines, and dark mode support.
diff_emailsCompare two email HTML versions — shows score changes, fixed issues, and introduced issues per client.
Parameter | Type | Required | Description |
| string | Yes | Original email HTML |
| string | Yes | Modified email HTML |
| enum | No | Input format |
check_deliverabilityCheck email deliverability for a domain — SPF, DKIM, DMARC, MX, BIMI records with a score and actionable issues.
Parameter | Type | Required | Description |
| string | Yes | Domain to check (e.g. |
EMAILENS_API_KEY)capture_screenshotsCapture real email screenshots across 21 clients in real browsers. Screenshots are hosted on CDN.
Parameter | Type | Required | Description |
| string | Yes | Email HTML source |
| enum | No | Input format |
| string[] | No | Filter clients |
| string[] | No |
|
| string | No | Name for the preview |
Free plan: 30 previews/day. Sign up
share_previewCreate a shareable link. Recipients see the full analysis without an account.
Parameter | Type | Required | Description |
| string | Yes | Email HTML source |
| string | No | Display title |
| enum | No | Input format |
Requires Dev plan ($9/mo). Share links expire after 7 days (Dev) or never (Pro).
Client | ID | Dark Mode | Notes |
Gmail |
| Yes | |
Gmail Android |
| Yes | |
Gmail iOS |
| Yes | |
Outlook 365 |
| Yes | |
Outlook Windows |
| No | |
Outlook Windows Legacy |
| No | Deprecated Oct 2026 |
Outlook iOS |
| Yes | New in v0.4.0 |
Outlook Android |
| Yes | New in v0.4.0 |
Outlook for Mac |
| Yes | New in v0.10.0 |
Apple Mail |
| Yes | |
Apple Mail iOS |
| Yes | |
Yahoo Mail |
| Yes | |
Yahoo Mail Android |
| Yes | New in v0.10.0 |
Yahoo Mail iOS |
| Yes | New in v0.10.0 |
Samsung Mail |
| Yes | |
Thunderbird |
| No | |
HEY Mail |
| Yes | |
Proton Mail |
| Yes | New in v0.10.0 |
AOL Mail |
| Yes | New in v0.10.0 |
Fastmail |
| Yes | New in v0.10.0 |
Superhuman |
| Yes |
bun install
bun run build
bun test
bun run typecheckMIT
If this saved you from an Outlook surprise, a star helps other email developers find it.
Unclaimed servers have limited discoverability.
If you are the server author, to access and configure the admin panel.
Create sandboxed public-unlisted or access-key-protected HTML previews through a remote MCP server.
Read, search, send, organize, draft and schedule email across your inboxes from any MCP client.
could-have-been-email MCP — wraps StupidAPIs (requires X-API-Key)
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