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How to Add a Signature in Outlook

Learn how to add a signature in Outlook.com. Step-by-step instructions, common issues to watch for, and how Signature Hound gives you Outlook-ready signatures without formatting problems.

Outlook is one of the most widely used email clients in the world — but it comes in two very different flavours: Modern Outlook (Outlook.com and the new Outlook desktop app) and Classic Outlook (the traditional desktop application, also known as Outlook for Windows or Outlook for Mac).

The way you add a signature — and how well that signature renders — differs significantly between the two. This guide covers both, so you can set up a professional signature no matter which version you’re using.

In this guide, we’ll cover:

Modern Outlook vs Classic Outlook: What’s the Difference?

Microsoft has been rolling out a redesigned New Outlook experience that aligns the desktop app with Outlook.com (the web version). If you’ve recently updated Windows 11 or Microsoft 365, you may already be using it.

Here’s how the two versions compare when it comes to email signatures:

Modern Outlook (Outlook.com / New Outlook):

✅ Accepts HTML signatures via direct copy-paste
✅ Hosted images display inline — no attachment issues
✅ Formatting stays consistent across email clients
✅ Multiple signatures, easy to switch when composing

Classic Outlook (Desktop App):

✅ Supports multiple signatures
✅ Works offline, deeply integrated with Microsoft 365
⚠️ Uses Word as its rendering engine — can strip styles or break layouts
⚠️ Images may appear as attachments if not hosted externally
⚠️ Requires HTML format mode to be enabled manually

The bottom line: Modern Outlook is significantly better for HTML signatures. It accepts a copy-paste of your rendered signature directly, preserving logos, fonts, and links. Classic Outlook has a more limited editor that can introduce formatting issues, especially with complex HTML.

How to Add a Signature in Modern Outlook (Outlook.com / New Outlook)

This applies to outlook.com in a browser and the New Outlook desktop app (available on Windows 11 and as an update to Microsoft 365).

  1. Open Outlook.com in your browser, or launch the New Outlook app.
  2. Click the Settings cog in the top-right corner.
  3. Select Mail from the left sidebar, then click Compose and reply.
  4. Scroll down to the Email signature section.
  5. Click New signature and give it a name.
  6. In the signature editor, paste your signature directly. If you’re using Signature Hound, open your signature preview in a browser, select all (Ctrl+A), copy (Ctrl+C), and paste it here.
  7. Under Select default signatures, choose your new signature for:
    • New messages
    • Replies/forwards
  8. Click Save.

Pro tip: Modern Outlook also lets you create multiple signatures and switch between them when composing. This is useful if you have different roles or want a shorter signature for replies.

How to Add a Signature in Classic Outlook (Desktop App)

This applies to the traditional Outlook desktop app — the version most commonly used in corporate environments with Microsoft 365 or older Office licences.

  1. Open Outlook on your Windows or Mac computer.
  2. Click File in the top-left menu, then select Options.
  3. In the left sidebar, click Mail, then click the Signatures… button.
  4. Click New to create a new signature and give it a name.
  5. In the editor at the bottom, paste your signature. For best results with HTML signatures, open your signature in a browser, select all and copy, then paste directly into the Outlook editor.
  6. Under Choose default signature, set your signature for:
    • New messages
    • Replies/forwards
  7. Click OK to save.

Important for Classic Outlook: Make sure “Compose messages in HTML format” is enabled. Go to File > Options > Mail and under Compose messages, set the format to HTML. Without this, Outlook will strip all styling from your signature.

Common Outlook Signature Issues

  • Signature not appearing on replies or forwards: In both Modern and Classic Outlook, the default setting may only add your signature to new messages. Make sure you explicitly set the signature for replies/forwards in the signature settings.
  • Formatting looks broken after pasting (Classic Outlook): Classic Outlook’s editor can add unwanted line breaks, change fonts, or strip colours. This is a known limitation of the editor. Using a signature generator like Signature Hound that produces Outlook-optimised HTML minimises these issues.
  • Images showing as attachments: This typically happens when images are embedded (base64) rather than hosted online. Always use a signature with hosted image URLs. Signature Hound hosts all images on a secure CDN to prevent this.
  • Signature stripping styles (Classic Outlook): Classic Outlook uses Microsoft Word as its rendering engine, which does not support many standard CSS properties. Signatures must use table-based layouts and inline styles to render correctly.
  • Different signature in the New Outlook app vs Outlook.com: The New Outlook desktop app and Outlook.com share the same signature settings when you’re signed in to the same Microsoft account. If you see different signatures, check that you’re signed in to the same account in both places.
  • Plain text mode stripping everything: If your Outlook is set to compose in plain text, all HTML formatting will be removed. Switch to HTML mode via File > Options > Mail > Compose messages in this message format: HTML.

The Easiest Way: Build and Install with Signature Hound

Outlook — especially Classic Outlook — is notoriously difficult to get right with HTML signatures. Fonts shift, images break, and layouts that look perfect in Gmail can fall apart completely in Outlook.

Signature Hound takes care of all of this:

  • All templates are tested and optimised specifically for both Modern and Classic Outlook.
  • Images are hosted on our secure CDN — no attachments, no broken image icons.
  • Table-based HTML ensures your layout stays consistent even in Classic Outlook’s Word-based renderer.
  • Share your signature with your whole team so everyone looks consistent, whether they’re on Outlook.com, the New Outlook app, or Classic Outlook.

Get started today.

From individuals to big business, we’ve made it easy to create perfect email signatures.

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