Definition
Outlook desktop builds emails with the Word engine, which ignores much modern CSS. Knowledge of MSO quirks is core to reliable Outlook rendering.
Best Practices
- Test in Outlook 2013-2019 and 365, the most common versions.
- Apply MSO conditionals for backgrounds and layout that Word ignores.
- Expect limited support for flexbox, grid, and padding on tables.
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Frequently Asked Questions
It uses the Word rendering engine rather than a browser engine.
Flexbox, grid, background sizing, border-radius and margins on many elements.
Use conditional comments and VML for background and layout fallbacks.