Create polished, Outlook-friendly email signatures for your team.
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Use Copy for Outlook to paste a working signature. The HTML option is only for developers editing the template.
The only reliable test
Send a real email to yourself at a different address (Gmail, iCloud, or another Outlook account) and view it in both light mode and dark mode. That's how recipients will see it.
Why do I see a white background?
Outlook's signature editor has a white canvas, and when you copy out of Outlook, that white canvas comes along on the clipboard. The signature HTML itself has no background — it's fully transparent. Don't judge it by pasting back out of Outlook; that test is misleading.
Do not paste the HTML code into Outlook's signature box — it will appear as raw text. Always use Copy for Outlook.
Root cause: Outlook sent the message as Rich Text (TNEF) instead of HTML. Gmail and most other clients can't read TNEF, so they strip the formatting, pack the original into a winmail.dat attachment, and show a broken fallback (missing icons, exposed URLs, no banner). This is a sender-side Outlook setting — no signature HTML can work around it.
New Outlook for Mac
Open a new message → Options tab → confirm the format is HTML. If it still arrives as winmail.dat, the cause is almost always a per-contact override synced from Exchange, or an admin transport rule on your Microsoft 365 tenant.
Quick isolation test: switch to Legacy Outlook (Help → Revert to Legacy Outlook) and send once. If it works there, the issue is in the new-Outlook send pipeline for that recipient and an admin needs to look at server-side rules.
Legacy Outlook for Mac
Per message: Message → Format → HTML.
Outlook for Windows (classic)
Per message: Format Text tab → HTML.
Global: File → Options → Mail → "When sending messages in Rich Text format to Internet recipients" → Convert to HTML Format.
Also open the recipient's contact card and confirm it isn't set to "Send Plain Text Only" or "Send using Outlook Rich Text format".
Outlook on the web / new Outlook for Windows
Sends HTML by default. If you still see winmail.dat, it's a server-side Exchange/Microsoft 365 transport rule and needs an admin to fix.