Install an HTML email signature in Outlook.
A complete guide for every flavor of Outlook in 2026: New Outlook for Windows & Mac, Classic Outlook desktop, Outlook on the Web, and Outlook mobile. Paste your HTML, set the defaults, done.
Which version of Outlook do you have?
Microsoft ships four distinct Outlook clients in 2026, and each has a slightly different signature workflow. Identify yours first:
New Outlook (Windows 11 / Mac)
Released 2024. Cleaner UI, web-based rendering engine. If your Outlook icon is the blue-and-white modern one and the layout feels more like Outlook on the Web, you have this version.
Classic Outlook (Windows desktop)
Outlook 2016 / 2019 / 365 desktop. Ribbon-based UI, uses Microsoft Word as the HTML rendering engine, which is why signatures from cheap generators break here.
Outlook on the Web
outlook.office.com (work / school) or outlook.live.com (personal Microsoft accounts). Browser-based, identical install flow regardless of OS.
Outlook Mobile (iOS / Android)
The mobile app only supports plain-text signatures. For HTML signatures on mobile, install via Outlook on the Web / desktop and rely on Microsoft 365 cloud sync.
New Outlook (Windows & Mac).
New Outlook uses the same web-based renderer as Outlook on the Web, so HTML signatures with modern CSS, web fonts, and inline images render reliably.
- 01
Open Outlook settings
In the top-right corner of the New Outlook window, click the gear icon to open the settings panel. On the mobile app, tap the menu (☰) in the top-left, then tap the gear icon at the bottom.
- 02
Go to Account → Signatures
In the settings panel, click Accounts in the left sidebar, then click Signatures. This is where every signature tied to your Outlook account lives: you can have multiple and switch between them.
- 03
Paste your HTML signature
Click + New signature, give it a name (e.g. "Main"), then click into the signature editor body. Press Ctrl + V (Windows) or ⌘ + V (Mac) to paste the HTML you copied from SmartMailing. The signature renders inline: colors, logo, and social icons should all appear.
- 04
Set the default for new emails and replies
Scroll down to "Select default signatures." Pick your new signature from the dropdown for both "For new messages" and "For replies/forwards." Click Save. Your signature will now auto-attach to every email you send from this account.
Classic Outlook desktop (Windows).
Classic Outlook uses Microsoft Word to render HTML, the trickiest email client in the world. SmartMailing's table-based output is built specifically to survive this renderer.
- 01
Open a new email
In Classic Outlook for Windows, click New Email in the top-left. You won't actually send anything: you just need the compose window to access the Signatures menu.
- 02
Open the Signatures dialog
In the new email window, click the Message tab in the ribbon, then click Signature → Signatures… This opens the Signatures and Stationery dialog where you manage every signature for every Outlook account on this machine.
- 03
Create a new signature
Click New, type a name (e.g. "Main"), and click OK. The new entry appears in the list above.
- 04
Paste your HTML signature
Click into the "Edit signature" box at the bottom of the dialog and press Ctrl + V to paste the HTML. Classic Outlook uses Word as its rendering engine, which is why HTML signatures from cheap generators often break here: SmartMailing's table-based output is built specifically to render correctly in this engine.
- 05
Set defaults and save
In the top-right of the dialog, pick the signature for "New messages" and "Replies/forwards." Click OK. The signature now auto-attaches to outgoing mail from the selected account.
Outlook on the Web.
Works identically on outlook.office.com (work / school) and outlook.live.com (personal Microsoft accounts).
- 01
Open Outlook on the Web
Go to outlook.office.com (work / school) or outlook.live.com (personal). Sign in if you're not already.
- 02
Open Settings → Mail → Compose and reply
Click the gear icon in the top-right, then in the settings panel pick Mail → Compose and reply. Scroll to the "Email signature" section.
- 03
Paste your signature
Give the signature a name, click into the editor body, and press Ctrl + V (Windows) or ⌘ + V (Mac) to paste. Outlook on the Web preserves HTML formatting, so the layout, colors, and logo all carry over.
- 04
Set defaults and save
Below the editor, pick your signature for "For new messages" and "For replies/forwards" from the dropdowns. Click Save at the bottom of the panel.
Outlook Mobile (iOS & Android).
The Outlook mobile app does not support full HTML signatures with images. The Signature setting inside the app is plain-text only. To use your HTML signature on mobile, you have two options:
- Recommended: install the HTML signature in Outlook on the Web (or desktop) on the same Microsoft 365 account. Microsoft's cloud-sync (rolling out through 2026) will use your web signature when you compose from the mobile app.
- Fallback: set a short plain-text signature in the mobile app (Settings → Signature) for mobile-composed emails, and rely on the full HTML version for desktop / web sends.
Pro tips & common pitfalls.
Things that will save you from broken images, missing colors, and the dreaded "signature looks fine in preview, broken in Outlook" surprise.
Don't use pure white or pure black backgrounds
Outlook (and most other clients) merge pure #ffffff or #000000 backgrounds with the email body in light or dark mode, which makes your signature look broken. The SmartMailing builder warns you about this; pick something slightly off (e.g. #ebebeb) so the signature stays visually distinct.
Host your logo on a real CDN
If your logo loads from a temporary URL (Dropbox preview, Google Drive share), recipients will eventually see a broken image. SmartMailing uploads logos to Supabase storage with permanent public URLs so old emails keep rendering correctly years later.
Test with a "send to yourself"
After installing, send a test email to a second account (preferably one on a different provider, e.g. a Gmail account if you installed in Outlook). Open it on both desktop and mobile to confirm the signature renders the way you expect.
Use one signature per account, not per device
Outlook stores signatures per account, not per machine. If you install on your work laptop, the same signature won't automatically sync to your phone: install separately on each device. (Outlook 365 sync for signatures is improving but still inconsistent in 2026.)
Frequently asked questions.
Will my HTML signature render the same in Classic Outlook and New Outlook?+
Can I install an HTML signature in the Outlook mobile app?+
Why is my pasted signature missing the logo / colors / social icons?+
How do I set different signatures for different Outlook accounts?+
Can I edit the signature later after installing?+
Don't have a signature yet?
Generate a clean, Outlook-safe HTML signature in under a minute. Free, no sign-up, no watermark, and the HTML is built specifically to render correctly in every version of Outlook covered above.
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