How do I add a signature in Outlook?

In Outlook desktop, go to File > Options > Mail > Signatures. Click New, name your signature, paste your content, then assign it as the default for new messages and/or replies under 'Choose default signature'.

Why does my Outlook signature look broken or have extra gaps?

Outlook renders signatures using Microsoft Word's HTML engine, not a browser. Tables must include border='0' cellpadding='0' cellspacing='0'. Images must have width set as both an HTML attribute and inline CSS (e.g., width='80' style='width:80px;max-width:80px;'). Image-only table cells need style='font-size:0;line-height:0' to remove the phantom gap below the image.

How do I change my Outlook signature?

Go to File > Options > Mail > Signatures, select your existing signature from the list, edit the content, then click OK to save.

Why is my Outlook signature not showing?

Two common causes: (1) the signature isn't assigned to your account — check File > Options > Mail > Signatures > Choose default signature. (2) Outlook is composing in Plain Text or Rich Text instead of HTML — change to HTML at File > Options > Mail > Compose messages in this format.

Outlook Signature: Complete Setup & Customization Guide

Outlook renders signatures using Microsoft Word's HTML engine — not a browser. That single fact explains every quirk: why CSS classes don't work, why images render with gaps, and why your signature looks correct in Chrome but breaks in Outlook. This guide covers setup steps for every Outlook version plus the technical requirements that make signatures actually render correctly.

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How Outlook Stores and Renders Signatures

Understanding the storage and rendering model prevents the most common Outlook signature problems.

Word HTML rendering engine

Outlook 2007–2021 and Microsoft 365 (classic) use the Microsoft Word HTML rendering engine. It does not support CSS floats, flexbox, CSS grid, or CSS class selectors. Multi-column layouts must be built with HTML tables. All CSS must be applied inline on each element — external stylesheets and <style> blocks are ignored.

Signature file storage

Signature files are stored at %AppData%\Microsoft\Signatures\. Outlook creates three files per signature: name.htm (for HTML email), name.rtf (for Rich Text), and name.txt (for Plain Text). You can back up and transfer signatures by copying this folder between machines.

Compose format requirement

Outlook must be set to compose in HTML format for your signature to render correctly. Go to File > Options > Mail > 'Compose messages in this format' and select HTML. If this is set to Plain Text or Rich Text, your HTML signature will not display.

New Outlook (2024/365 on Windows)

The new Outlook app (released 2024, the cloud-based version) uses a different rendering engine and syncs signatures to the cloud. Signatures are managed at Settings > Accounts > Signatures rather than File > Options > Mail > Signatures. It does not share signatures with classic Outlook.

How to Add a Signature in Outlook Desktop

Applies to Outlook 2016, 2019, 2021, and Microsoft 365 (classic) on Windows and Mac.

Open Signature Settings

Windows: File → Options → Mail → Signatures.
Mac: Outlook → Preferences → Signatures.

Create a New Signature

Click New and give it a name — this is just an internal label (e.g. “Main” or your name).

Paste Your Signature

Click inside the editor box and paste with Ctrl+V. If pasting a SignForge signature, the table-based HTML and inline styles will be preserved correctly by Outlook's editor.

Assign a Default per Account

Under Choose default signature, select your email account from the dropdown, then assign your signature to “New messages” and optionally “Replies/forwards”. Repeat for each additional account.

Save and Verify

Click OK. Open a new compose window — your signature should appear automatically.

How to Add a Signature in Outlook Web (OWA)

Outlook Web App (outlook.com or corporate OWA) stores signatures independently from the desktop app. You need to set it up separately.

Open Settings

Click the gear icon (top right), then View all Outlook settings.

Navigate to Signature

Go to Mail → Compose and reply. Scroll to the Email signature section.

Paste Your Signature

Click inside the editor and paste with Ctrl+V or Cmd+V. OWA preserves rich HTML formatting including images and icons.

Set Auto-Insert

Enable “Automatically include my signature on new messages” and “on replies” if needed.

Save

Click Save.

How to Add a Signature in Outlook Mobile

The Outlook mobile app (iOS and Android) supports plain-text signatures set on device. For a rich HTML signature, use the desktop or web app — signatures set there will send correctly even from mobile.

Open App Settings

Tap your profile photo (top left), then the gear icon (bottom left).

Find Signature

Tap Signature.

Toggle and Enter

Toggle Per Account Signature if you manage multiple accounts. Type your plain-text signature. The app saves automatically on exit.

HTML Technical Requirements for Outlook

These requirements apply because Outlook uses Word's HTML engine. Signatures generated by SignForge already comply with all of these.

Use tables for layout — not divs

CSS floats, flexbox, and grid are not rendered by the Word engine. Every multi-column layout must use HTML tables. Add border="0" cellpadding="0" cellspacing="0" to every <table> element to eliminate default cell spacing.

Inline CSS only — no class selectors

Outlook ignores CSS classes and <style> blocks. Every style property must be applied directly on each element: style="color:#1a1a1a;font-size:14px;font-family:Arial,sans-serif".

Fix the image DPI rendering bug

Outlook at high DPI settings can double the displayed size of images. Fix by setting width as both the HTML attribute AND inline CSS: <img width="80" style="width:80px;max-width:80px;">. The max-width prevents it from expanding on HiDPI screens.

Fix the image gap bug

By default, images inside table cells have a phantom gap below them caused by line-height. For any table cell containing only an image, add: style="font-size:0;line-height:0" to the <td> element.

Use web-safe fonts only

Custom fonts (Google Fonts, Adobe Fonts) cannot be loaded in email. The reliable stacks are: Arial, Helvetica, sans-serif (sans-serif) or Georgia, 'Times New Roman', serif (serif). Fallback to system fonts always.

Host images externally

Do not embed images as base64 in email signatures — they dramatically increase file size and may trigger spam filters. Use a publicly accessible URL (your company website, CDN, or image host).

Exchange Transport Rules & Corporate Signatures

In corporate environments using Microsoft Exchange or Microsoft 365 for Business, IT administrators can configure Exchange transport rules (also called mail flow rules) that automatically append a standardized footer or disclaimer to all outgoing email.

This happens server-side after your email is sent — you cannot see, edit, or disable these footers from your Outlook client. Your personal signature appears first, then the corporate footer is appended by the Exchange server before delivery.

If your organization uses transport rules, coordinate your personal signature design with your IT team to avoid duplication — for example, if the server appends the company address and legal disclaimer, you don't need to include them in your personal signature.

Troubleshooting Outlook Signature Problems

Signature not appearing in new emails

Go to File > Options > Mail > Signatures. Under 'Choose default signature', confirm your email account is selected and a signature is assigned to 'New messages'. Also check that Outlook is composing in HTML: File > Options > Mail > Compose messages in this format: HTML.

Images appear too large or oversized

Outlook scales images based on DPI settings. Set width as both an HTML attribute and inline CSS: <img width="80" style="width:80px;max-width:80px;">. Without the inline CSS, Outlook ignores the HTML attribute at high DPI.

Unwanted gap below images in the signature

Add style="font-size:0;line-height:0" to the <td> element containing the image. The gap is caused by the default line-height in the table cell, not by the image itself.

Formatting broken — extra spaces between table columns

All tables must have border="0" cellpadding="0" cellspacing="0" attributes. Without these, Outlook applies default HTML table spacing that breaks multi-column layouts.

Signature appears in plain text instead of HTML

Two checks: (1) File > Options > Mail > Compose messages in this format must be set to HTML. (2) When replying to a plain-text email, Outlook may downgrade your compose format — change the format of that reply to HTML via Format Text > HTML in the compose ribbon.

Signature not showing in replies

In Signatures settings (File > Options > Mail > Signatures), set your signature for 'Replies/forwards' in the 'Choose default signature' section. This is separate from 'New messages'.

Frequently Asked Questions

Can I have multiple Outlook signatures?

Yes. Create multiple signatures under File > Options > Mail > Signatures. When composing, click Insert > Signature to switch manually. You can also set different defaults for new messages vs. replies.

Can I have different signatures for different email accounts?

Yes. In Signatures settings, the 'Choose default signature' section has an 'E-mail account' dropdown. Select each account and assign its own default signature separately.

How do I back up my Outlook signatures?

Copy the folder at %AppData%\Microsoft\Signatures\ to another location. This contains your .htm, .rtf, and .txt signature files. Paste it into the same path on a new machine to restore.

Does Outlook support HTML email signatures?

Yes, but with restrictions. Outlook supports table-based HTML with inline CSS. It does not support CSS floats, flexbox, grid, or <style> blocks. All layout must use HTML tables; all styling must be inline.

How do I remove a signature from Outlook?

Go to File > Options > Mail > Signatures. To delete: select the signature and click Delete. To stop auto-insert without deleting: set 'New messages' and 'Replies/forwards' dropdowns to '(none)'.

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