Why your signature breaks in Outlook

Outlook renders through Microsoft Word, not a browser. Here is what that changes, and the five faults it causes most often.

If a signature looks right everywhere and wrong in Outlook, the cause is almost always the same: Outlook on Windows does not use a browser engine. It renders mail through Microsoft Word.

The five faults this causes

The logo is enormous

Word sizes an image from its own pixels unless the tag carries width and height attributes. CSS alone is not enough. This is the single most common fault.

Everything is stacked in one column

The layout used flexbox or CSS grid. Word supports neither and falls back to stacking. Only a table produces columns.

Spacing collapsed

Word handles margins on <div> elements poorly. Padding on a table cell works.

The whole block is far too wide

The design relied on max-width, which Word ignores. Use a fixed pixel width on the cell instead.

The animated logo does not move

Word does not animate. Outlook on Windows shows the first frame of a GIF and stops there. Nothing is broken and there is no setting to change; design the first frame to stand alone.

Fonts changed

The signature asked for a webfont. Email cannot load one. Only fonts already installed on the reader's machine will show, which in practice means Arial, Helvetica, Georgia, Verdana, Tahoma, Trebuchet MS and Times New Roman.

A trap worth knowing

A font stack written with double quotes, such as Georgia, "Times New Roman", serif, ends the style="…" attribute early when it is written into HTML. Everything after it in that style block is silently discarded, so colours and alignment vanish for no visible reason. Written with single quotes it is fine. Hand-built signatures hit this constantly.

How to test properly

A browser preview proves nothing about Outlook. Send yourself a real message and open it in the actual client, on Windows if that is what your recipients use. Check it once with images blocked and once in dark mode.

More guides

• Add your signature in Outlook
• Add your signature in Gmail
• Add your signature in Apple Mail
• Email signature best practices

Last updated 2026-08-31.