How to Limit Outlook Mobile Signature HTML to a Single Logo Image

When you set up an email signature in Outlook Mobile, the app may automatically convert your carefully designed HTML signature into a cluttered block of raw code or multiple broken images. This problem occurs because Outlook Mobile does not support complex HTML tables, multiple images, or embedded CSS the way the desktop version does. This article explains how to strip your signature HTML down to a single logo image that displays correctly on any mobile device. You will learn the exact HTML structure to use, how to test it, and what to avoid.

Why Outlook Mobile Rejects Complex Signature HTML

Outlook Mobile uses a limited HTML renderer that strips out CSS, JavaScript, and most structural tags. When the app encounters a signature with nested tables, multiple images, or font styling, it either removes those elements entirely or shows the raw HTML source code to the recipient. This behavior is by design to reduce security risks and keep messages lightweight on mobile networks.

The core limitation is that Outlook Mobile only reliably renders a single inline image with basic attributes. Any additional images, links, or formatting will likely be discarded. For a corporate logo that must appear consistently across all replies and forwards, you need a signature that contains nothing more than one <img> tag.

What Outlook Mobile Supports vs. Strips

Outlook Mobile preserves the following HTML elements in signatures: <img> with src, width, height, and alt attributes; plain text; and simple line breaks (<br>). It strips or breaks the following: <table>, <tr>, <td>, <div>, <span>, <style>, <link>, <script>, <font>, and any CSS classes or IDs. Knowing this boundary is the first step to building a signature that works.

Steps to Create a Single-Image Signature for Outlook Mobile

1. Upload your logo to a public HTTPS server
   Your logo image must be accessible from the internet over HTTPS. Use a company web server, a cloud storage service with a public link, or a dedicated image hosting platform. The URL must start with https://. Outlook Mobile blocks HTTP images to prevent mixed content warnings. The image file should be under 100 KB to load quickly on mobile networks.
2. Resize the image to the correct dimensions
   Use an image editor to set the logo width to 200 pixels and height proportional to the original aspect ratio. A logo wider than 300 pixels may be clipped by Outlook Mobile on smaller screens. Save the file as PNG or JPEG. Do not use GIF or BMP formats because Outlook Mobile may not render them reliably.
3. Write the minimal HTML signature code
   Open a plain text editor such as Notepad. Type the following code exactly, replacing the URL and dimensions with your own values:

   <img src="https://yourcompany.com/logo.png" width="200" height="60" alt="Your Company Logo">

   Do not add any other tags, line breaks, or spaces around the <img> tag. The signature must contain only this single line of HTML.

4. Copy the HTML into Outlook Mobile signature settings
   On your iPhone or Android device, open Outlook Mobile. Tap your profile picture or the account icon in the top left corner. Tap the gear icon to open Settings. Scroll down and tap Signature. Under the email account you want to modify, tap Signature. Delete any existing content. Paste the single <img> tag you created. Tap Save in the top right corner.
5. Send a test email to verify the signature
   Compose a new email to your own work address or a test account. Do not add any text in the body. Send the message. Open the received email on a desktop email client and on the Outlook Mobile app. Check that the logo appears as a single image with no broken link icon or raw HTML code surrounding it.

What to Do If the Signature Still Displays Incorrectly

Outlook Mobile Shows the HTML Code Instead of the Image

This happens when the signature contains extra characters or tags. Open the signature again in Outlook Mobile. Delete everything. Paste only the single <img> tag. Do not add a blank line before or after it. Save and test again.

The Logo Appears as a Broken Image Icon

The image URL is not accessible or is blocked. Verify that the URL starts with https:// and that the file is publicly reachable. Open the URL in a mobile browser to confirm it loads. If the URL works in a browser but not in the signature, the server may be blocking hotlinking. Configure your web server to allow cross-origin requests or move the image to a different host.

The Image Is Too Large or Stretched

Outlook Mobile ignores width and height attributes if the image file itself is larger than 500 pixels wide. Resize the source image to exactly 200 pixels wide using an image editor. Re-upload the resized file and update the src URL in the signature.

The Signature Appears in Desktop Outlook but Not on Mobile

Outlook Mobile does not sync signatures with the desktop version. You must configure the signature separately on each device. Follow the same steps on every iPhone or Android device where you want the logo to appear.

Single Image Signature vs. Full HTML Signature: Key Differences

Item	Single Image Signature	Full HTML Signature
Rendering on Outlook Mobile	Displays the logo reliably every time	Often shows raw HTML or a blank space
Complexity	One line of code, no CSS or tables	Multiple tables, fonts, colors, and images
File size in email	Under 100 KB for the image	Can exceed 500 KB with embedded assets
Setup time	5 minutes per device	30 minutes plus testing on multiple clients
Risk of breakage after updates	Low — only one element to break	High — Outlook mobile updates often strip complex HTML

You can now create an Outlook Mobile signature that contains only a single logo image and displays correctly on every reply and forward. After setting up the signature, test it by sending a message to a colleague using a different mobile platform. For advanced control, consider using Microsoft Exchange transport rules to append a mobile-friendly signature server-side instead of relying on client-side settings.