Why your signature breaks in Outlook (and what we do about it)
Outlook still uses Microsoft Word as its rendering engine. We explain what that means and the techniques we use to ship signatures that survive it.
Tomás Reyes
· Senior front-end engineer ·
May 9, 2026
·
7 min read
The Word engine problem
Outlook for Windows uses MS Word to render HTML email — including signatures. Word ignores most modern CSS, including flexbox, grid, gradients, and even some basic positioning.
What still works
Tables, inline styles, named colours, web-safe fonts, and pixel-based dimensions. That's the menu. Everything we ship sticks to it.
MSO conditional comments
When we absolutely need a workaround, we use Microsoft's `