How to Add an HTML Signature to Outlook (Mac & Windows) in 2025

Outlook is notorious for breaking email signatures. If you've ever pasted a beautiful signature into Outlook only to see it distorted, blurry, or misaligned, you're not alone. Outlook uses Microsoft Word's rendering engine, which interprets HTML differently than web browsers.

In this guide, we'll show you exactly how to install an HTML signature on Outlook for Windows, Mac, and Web (Outlook.com/Office 365) so it looks perfect every time.

Why is Outlook So Difficult?

Unlike Gmail or Apple Mail, Outlook for Windows converts your HTML into VML (Vector Markup Language) in the background. This often breaks:

• Rounded corners (border-radius)
• Background images
• Custom fonts
• Padding and margins
• GIF animations (in older versions)

The Solution: You need code that is specifically optimized for Outlook's rendering engine. The easiest way to get this is by using a dedicated tool like EmailSignature.pro that automatically generates the necessary VML fallback code for you.

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Method 1: Outlook for Windows (The "File Switch" Method)

This is the most reliable way to install a signature on the classic Outlook desktop app.

Step 1: Open the Signatures Folder

1. Press Win + R on your keyboard to open the Run dialog.
2. Paste this path: %AppData%\Microsoft\Signatures
3. Click OK. This opens the folder where Outlook stores signatures.

Step 2: Create Your Files

If you are designing your signature manually, you need an .htm file.

• Pro Tip: If you use our Free Email Signature Generator, simply download the HTML file provided.

Step 3: Replace the File

1. Drag and drop your .htm file into this folder.
2. If you want to replace an existing signature, rename your new file to match the old one exactly (e.g., MySignature.htm).

Step 4: Activate in Outlook

1. Open Outlook.
2. Go to File > Options > Mail > Signatures.
3. You should see your new signature in the list.
4. Set it as the default for New Messages and Replies/Forwards.
5. Click OK.

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Method 2: Outlook for Mac

Outlook for Mac (especially the "New Outlook" mode) behaves more like a web browser, but still has quirks.

Step 1: Generate Your Signature

Create your signature using a compatible generator. Copy the HTML content to your clipboard.

Step 2: Open Preferences

1. Open Outlook for Mac.
2. Click Outlook in the menu bar > Settings (or Preferences).
3. Click Signatures.

Step 3: Paste and Save

1. Click the + button to create a new signature.
2. Paste your signature into the box.
3. Crucial Step: A clipboard icon usually appears when pasting. Click it and select "Keep Source Formatting". If you don't do this, Outlook may strip your styling.
4. Assign the signature to your account.

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Method 3: Outlook on the Web (Office 365)

This method allows your signature to show up when you access email via a browser.

1. Go to Outlook.com or Office.com and sign in.
2. Click the Gear icon (Settings) in the top right.
3. Search for "Email signature" or navigate to Mail > Compose and reply.
4. Paste your signature design.
5. Ensure "Insert signature before quoted text..." is checked for cleaner replies.
6. Click Save.

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Common Outlook Issues & Fixes

Issue: Images are blurry or resized

Fix: Outlook tries to rescale images based on screen DPI. Always define the explicit width and height in your HTML <img> tags.

• Bad: <img src="logo.png">
• Good: <img src="logo.png" width="200" height="50">

Issue: White lines appear between images

Fix: This is a line-height issue. Ensure your HTML tables include border-collapse: collapse; and set display: block; on images.

Issue: Custom fonts aren't showing

Fix: Outlook only supports clear standard fonts (Arial, Times, Verdana). If you use a Google Font, Outlook will revert to Times New Roman. You must wrap your text in a generic font stack fallback or use a tool that inserts the correct MSO conditional comments.

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Summary

Outlook requires patience and precise coding. Do not expect standard web HTML to work 100%.

• For best results: Use EmailSignature.pro to generate code that is pre-tested for all versions of Outlook.
• For Windows: Use the %AppData% folder method.
• For Mac: Remember "Keep Source Formatting".

Ready to slay your Outlook signature issues? Create your professional Outlook signature now.