Outlook Email HTML Lint - Classic vs New

Classic Outlook renders with the Word engine, the new Outlook with WebView2. Lint one email file against both at once, line by line, before you send.

Install

npx @readystack/outlook-email-html-lint file

Node 18+. The same 33 rules as the VS Code extension, from a terminal or CI.

Free

• Check the open email file against both Outlook engines and get every finding with a suggested fix - no key, no limit.
• --rules lists every rule

With a licence ($29 once)

• Scan the whole template library in one pass, export a client-ready CSV/JSON/HTML report, and emit CI output that can stop a broken template.

@readystack/outlook-email-html-lint --dir ./templates --report html --out report.html

Email on Acid Basics is $99/month and Litmus Core starts at $500/month (checked 2026-09-07).

Use from an AI agent (MCP)

Claude Code · Cursor · Windsurf · any MCP client - add to your MCP config:

{ "mcpServers": { "outlook-email-html-lint": { "command": "npx", "args": ["-y", "@readystack/outlook-email-html-lint", "--mcp"] } } }

Tools: check_text and check_file (free) · check_dir (licence). The agent gets every finding with the line number.

Use in CI

- name: Outlook Email HTML Lint - Classic vs New
  run: npx -y @readystack/outlook-email-html-lint --dir . --ci

(container: docker run --rm -v "$PWD:/work" getreadystack/outlook-email-html-lint --dir /work --ci)

The folder sweep, reports and CI mode need one licence — one payment, no subscription. Set READYSTACK_LICENSE=<key> or run --license <key> once.

Get a licence