eslint-plugin-mso-email

eslint-plugin-mso-email

ESLint plugin for Outlook/HTML email markup: MSO conditional comments, Outlook CSS properties, VML namespaces, and layout table accessibility.

Extracts conditional comments into a virtual file for AST-based rules, and lints full HTML documents for MSO CSS, VML, and table semantics.

Installation

npm install eslint-plugin-mso-email --save-dev

Requires ESLint 9+ (flat config) and Node.js 22+.

Quick Start

// eslint.config.js
import mso from 'eslint-plugin-mso-email';

export default [mso.configs.recommended];

This lints **/*.html, **/*.amp, and **/*.ampscript files.

Rules

All rules use the mso/ plugin prefix.

Rule	Default	Fixable	Description
mso/valid-mso-condition	error	partial (deterministic typos)	Validate MSO conditional opener syntax
mso/matching-mso-endif	error	no	Match openers and [endif] closers
mso/matching-mso-endif-type	warn	yes	Match closer variant to opener style
mso/no-unknown-mso-property	warn	partial (typo hints)	Disallow unknown mso-* CSS properties
mso/vml-requires-namespace	warn	yes	Require xmlns:* on html when using VML
mso/no-unknown-vml-tag	warn	yes	Disallow unknown VML tag names
mso/no-unknown-vml-attribute	warn	partial (typo hints)	Disallow unknown VML attributes
mso/table-presentation-role	warn	yes	Require role="presentation" on layout tables

Fixable legend

Value	Meaning
yes	ESLint can auto-fix every reported violation for that rule (with default options).
partial (deterministic typos)	Auto-fix only when the parser returns a single deterministic replacement for the condition substring (for example mos → mso). Invalid operators, unknown versions, and ambiguous conditions are reported without a fix.
partial (typo hints)	Auto-fix only when the property, tag, or attribute name has a close allowlist match within edit distance. Unknown names with no hint are still reported, but not auto-fixed.
no	Report only — inserting or removing structural comment markers is unsafe.

License

MIT