If your beautifully designed email arrives in Outlook as a stretched, square-cornered, overlapping mess, you've met the most infamous quirk in email development: Outlook for Windows doesn't use a browser engine to render email — it uses Microsoft Word.Since Outlook 2007, the desktop versions (2007 through 2019/2021, and classic Microsoft 365) render HTML through Word's engine, which was never meant to display web pages.

What Word's engine ignores

  • max-width — the property responsive layouts depend on. Your 600px container becomes full-width soup.
  • border-radius — every rounded button renders square.
  • background-image on divs and table cells — background images silently disappear.
  • display: flex and grid — no modern layout at all. Even float support is shaky.
  • Reliable padding on div and p — spacing must live on table cells.

How working emails handle it

Emails that render correctly in Outlook are built from nested <table> elements — the one structure Word lays out predictably — plus two Outlook-specific tricks:

Ghost tables. Since Outlook ignores max-width, you wrap fluid content in a fixed-width table that only Outlook sees, using conditional comments: <!--[if mso]><table width="600">…<![endif]-->. Other clients skip the comment; Outlook gets its rigid skeleton.

VML. Rounded buttons and background images are recreated for Outlook in Vector Markup Language, a legacy Microsoft format — again inside conditional comments.

The practical fix

Nobody should hand-write ghost tables in 2026. Frameworks like MJML generate all of this automatically from a simple layout description. That's exactly how our free email template builder works: you design visually, and the export is table-based HTML with every Outlook fallback already in place. Start from a free template and test it in your own Outlook to see.