Microsoft 365 - Emails with HTML formatting do not always display as expected

This document explains why some emails with HTML formatting do not always display as expected in desktop Outlook clients such as Outlook for Windows/Mac.

Outlook and Word HTML

Starting with Outlook 2007, Outlook has been only using the Word engine to display and create HTML-formatted emails. This does create some display issues, but now Outlook only has to support a single HTML engine (email editor), which makes developing easier and allows for more consistent behavior across your email experience. You do not need to have Microsoft Word installed for Outlook to use the Word HTML engine.

What doesn't always display correctly?

Some noticeable display issues are:

  • GIF images don't animate
  • Flash objects display as a red "X"
  • "Advanced" CSS formatting support
  • HTML accessibility support

Why aren't all HTML and CSS standards supported?

Most features that aren't supported fall under two categories:

  • The feature could pose a security risk
  • The feature isn't relevant to reading mail

You can contact Microsoft directly to make a case for supporting a specific feature in Office 365, by submitting your idea to Microsoft's User Voice site at

How to work around

If you open an email message and its contents are displaying incorrectly, Outlook will give you the option to open the message in a web browser.

If you are creating an email message, here are a few tips to make sure it displays correctly:

  • Since only the first frame of a GIF animation loads, make sure it communicates the main message of the graphic.
  • Make sure that the design's integrity doesn't rely solely on CSS to work.
  • Specify an increased amount of leading (space between lines of text).
  • Avoid using list items, because Outlook does not support them. Instead, use the bullet symbol.

For more information

See the following support document:

Keywordsmicrosoft office365 o365 m365 microsoft 365 email client html formatting display wrong outlook 2019 2016 proplus windows desktop for mac   Doc ID54428
OwnerO365 S.GroupMicrosoft 365
Created2015-07-28 10:32:29Updated2023-02-02 09:22:57
SitesDoIT Help Desk, Microsoft 365
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