Definition
Outlook desktop renders email with the Word engine, which ignores many modern CSS features. Layout relies on tables, inline styles, and conditionals.
Providing VML or image fallbacks handles backgrounds Outlook ignores.
Outlook's CSS limits force a defensive approach, relying on tables and inline styles. Conditionals and VML handle the gaps. Testing the versions your audience uses prevents the most common desktop failures.
What Outlook Supports
Use nested tables and inline styles for Outlook.
Expect limited flexbox, grid, and modern CSS.
Why It Matters
Outlook's CSS limits force a defensive approach to email design. Understanding them prevents the most common desktop rendering failures.
Best Practices
- Use nested tables and inline styles for Outlook.
- Provide VML or image fallbacks for backgrounds.
- Test Outlook 2013 plus and 365 before release.
- Keep conditional code documented.
- Align Outlook and modern versions.
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Related Glossary Terms
Above the Fold in Email
Above the fold in email refers to the content visible to a recipient before they scroll, a critical area for first impressions and primary calls to action.
Accessible CTA (Email)
An accessible CTA is a button or link coded with sufficient colour contrast, visible focus states, descriptive screen-reader text, and a minimum touch target of 44×44 pixels.
Adaptive Design
Adaptive design in email uses predefined layouts that adjust to specific device or client widths, rather than fluidly resizing to every possible screen.
AI-Generated Content in Email
AI-generated content in email is copy, images, code or subject lines produced by artificial intelligence tools to speed up campaign production and testing.
Alt Text
Alt text is the written alternative to an image in an email, displayed when images are blocked, slow to load, or consumed by screen readers.
Autoplay Video in Email
Autoplay video in email refers to the limited ability to play video content automatically when an email is opened, using specific client-supported techniques.
Frequently Asked Questions
Flexbox, grid, fluid layout, and consistent margin on tables. Outlook's CSS limits force a defensive approach, relying on tables and inline styles.
Only where present, and it ignores many responsive tricks. Conditionals and VML handle the gaps.
Code defensively: tables, inline styles, and conditionals. Testing the versions your audience uses prevents the most common desktop failures.
It is a legacy design decision. Outlook's CSS limits force a defensive approach, relying on tables and inline styles.
No, test the versions your audience uses. Conditionals and VML handle the gaps.