Definition
Outlook HTML conditionals are comment blocks Outlook reads to include or exclude markup, letting you ship Outlook-specific tables and styles.
Other clients treat them as comments and ignore them.
Outlook conditionals let you ship client-specific code safely, targeting the Word engine without breaking other clients. They are treated as comments by everyone else. Validating the final HTML prevents malformed conditionals from leaking content.
Using Conditionals
Wrap Outlook-only markup in conditional comment blocks.
Provide a modern fallback outside the conditional.
Why It Matters
Outlook conditionals let you ship client-specific code safely. Understanding them is essential for professional, Outlook-safe email.
Best Practices
- Wrap Outlook-only markup in conditional comment blocks.
- Provide a modern fallback outside the conditional.
- Validate the final HTML to catch unclosed conditional comments.
- Keep conditional code documented.
- Test in Outlook and modern clients.
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Frequently Asked Questions
They are treated as comments by non-Outlook clients, so yes. Outlook conditionals let you ship client-specific code safely, targeting the Word engine without breaking other clients.
Yes, using version-aware conditionals. They are treated as comments by everyone else.
No, they are ignored there, which is the point. Validating the final HTML prevents malformed conditionals from leaking content.
Its Word engine needs bespoke markup. Outlook conditionals let you ship client-specific code safely, targeting the Word engine without breaking other clients.
Only if malformed or unclosed. They are treated as comments by everyone else.