Email signature generator › Outlook for Mac

How to add an HTML signature in Outlook for Mac

Outlook for Mac shares a name with Outlook for Windows and almost nothing else. It renders HTML with WebKit, the same engine as Safari, which means your signature will look better here than where it counts.

Setting it

1. Outlook menu → Settings → Signatures.
2. + to create one. The editor is rich text: there is no source view, so you paste rendered content.
3. Under Choose default signature, set which account uses it and whether it goes on new messages, replies, or both.

To get designed HTML in, open your signature in Safari, select all, copy, and paste into the signature editor. Safari's clipboard preserves inline styles and table structure well.

The trap

Because Outlook for Mac uses WebKit, a signature built with modern CSS will look perfect to you and break for a colleague on Outlook for Windows, which renders incoming HTML with the Microsoft Word engine. Word ignores flexbox, grid, float, background images on most elements, and negative margins. A design that relies on any of those is not broken on your machine — it is broken on theirs, invisibly.

The rule is to build for Word and accept that it looks the same, not better, on the Mac. Tables with inline styles, explicit widths in pixels, spacing done with cell padding.

The new Outlook for Mac and profile sync

Signatures created in the new Outlook for Mac are stored with the account and sync to Outlook on the web for the same mailbox. Signatures created in the older build live only on that machine. If a signature you set on the Mac does not appear when you open the web client, you are on the older build — and the fix is to set it again in the web client rather than trying to sync it.

Images pasted from Safari

When you copy a rendered signature from Safari, images referenced by URL stay as links. Images that were data URIs in the source may be converted to attachments by Outlook on send, which is what produces the paperclip icon on your messages. If every message you send shows an attachment you did not add, the signature logo is the usual culprit.

Testing across the two Outlooks without two machines

The difficulty with Outlook for Mac is that you cannot see the failure from where you are sitting. Your signature looks correct in your own compose window and in your own sent folder, because both use WebKit.

The cheapest reliable test is to send the signature to a colleague on Windows and ask for a screenshot. The second cheapest is an Outlook.com web account, which is not the Word engine but shares much of Microsoft's sanitising behaviour and will catch the grosser problems. Do this once, when you build the signature, and then not again until you change it.

The three things that break most often

Widths in percentages. The Word engine handles percentage widths on tables unpredictably. Set widths in pixels on the table and on each cell, and cap the whole signature at around 500 pixels so it does not force a horizontal scroll in a narrow reading pane.

Spacing done with margin. Replace it with cell padding or with an empty row of a fixed height. Margin on a div is one of the first things Word discards.

Rounded corners and shadows. They simply do not render, and a design whose structure depends on them collapses into flat rectangles. Use them only where their absence still leaves something sensible.

Where the file lives, if you need it

Older Outlook for Mac builds keep signatures inside the application's own support folder in your user library, one file per signature. It is occasionally useful to know when a signature will not delete or has become corrupted, but editing those files by hand is not a supported path and Outlook can rewrite them without warning. Prefer rebuilding the signature in the interface.

Frequently asked questions