Definition
A bulletproof background renders a background image in Outlook desktop, which ignores CSS backgrounds, by layering VML inside conditional comments alongside a CSS fallback.
A fallback background colour ensures readability even where images are blocked.
Bulletproof backgrounds are how you get reliable full-bleed design in Outlook, which ignores CSS backgrounds. A VML layer for Outlook plus a CSS fallback for modern clients covers everyone. A colour fallback keeps readability where images fail.
How It Works
VML inside an Outlook conditional paints the background for Outlook.
CSS background-image handles modern clients, with a colour fallback.
Why It Matters
Bulletproof backgrounds are how you get reliable full-bleed design in Outlook. Understanding the technique makes your email look right everywhere.
Best Practices
- Enclose the VML in an Outlook conditional.
- Pair with a CSS background-image and background-size where supported.
- Provide a fallback background colour that reads clearly.
- Test in Outlook and modern clients.
- Keep image file sizes reasonable.
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Related Glossary Terms
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Accessible CTA (Email)
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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
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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
A VML layer for Outlook plus CSS for modern clients and a colour fallback. Bulletproof backgrounds are how you get reliable full-bleed design in Outlook, which ignores CSS backgrounds.
It adds markup, but it is the reliable way to get full-bleed images into Outlook. A VML layer for Outlook plus a CSS fallback for modern clients covers everyone.
Only where Outlook rendering matters; otherwise CSS suffices. A colour fallback keeps readability where images fail.
Outlook ignores CSS backgrounds on many elements. Bulletproof backgrounds are how you get reliable full-bleed design in Outlook, which ignores CSS backgrounds.
Readability when images do not load. A VML layer for Outlook plus a CSS fallback for modern clients covers everyone.