Shared Mailbox signature

Question

Hello Guys,

I want to change a Companys shared mailbox signature in the exchange admin center, but it doesn't take the picture. I did everything right and also put it in html format but it won't take the picture in the signature. Any solutions to this. I havent tried any exchange rules yet

Answer 1

Hi Besart Sylmetaj,

Thank you for posting your question on the Microsoft Q&A forum.

Based on your description, it appears you have attempted to include an image in your shared mailbox signature using HTML, but the image is not rendering as expected even after trying multiple approaches.

As the Q&A answer correctly noted, one of the most common causes of this issue is that the image is not hosted on a publicly accessible URL. When configuring a signature via the Exchange Admin Center, images referenced via an <img src="..."> tag must point to a publicly reachable HTTPS location.

That said, I would like to check: have you tried embedding the image directly using Base64 encoding? This approach embeds the image data inline within the HTML itself, which means the image does not need to be hosted externally.

Here is the general process:

1. Convert your image to a Base64 string using a tool such as Base64 Image Encoder
   Note: This information is provided as a convenience to you. These sites are not controlled by Microsoft, and Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please ensure that you fully understand the risks before using any suggestions from the above link.
2. Insert the resulting string into your HTML using the following format:

<img src="data:image/png;base64,YOUR_BASE64_STRING_HERE" alt="Company Logo" width="200">

Important note: If you are applying this signature via a mail flow rule (transport rule) in EAC, please be aware that the disclaimer field has a maximum limit of 5,000 characters, including all HTML markup. Base64 strings for images can be quite large, so the image may need to be small (e.g., a compact logo) to stay within this limit.

If you are trying to use a transport rule to add the signature, you may also find this article helpful: https://learn.microsoft.com/en-us/exchange/policy-and-compliance/mail-flow-rules/signatures

I hope this helps.

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Answer 2

If the picture in the shared mailbox signature is not displaying, there are a few things to consider:

1. Image Hosting: Ensure that the image is hosted on a publicly accessible server. Use the <IMG> tag to point to the image URL. For example:

      <IMG src="http://your-image-url.com/image.png" alt="Company Logo">
   

   Note that Outlook and Outlook on the web block external content by default, so users may need to download the blocked content manually.
2. Testing: After setting up the signature, send a test email to verify that the image appears correctly. Sometimes, it may not display in the signature preview but can appear in actual emails.
3. HTML Format: Make sure that the HTML format is correct and that there are no errors in the code that might prevent the image from loading.
4. Exchange Rules: If you haven't tried using Exchange rules yet, consider creating a rule to apply the signature to all outgoing emails. This can sometimes resolve issues with signatures not being applied correctly.

If these steps do not resolve the issue, you may want to look into third-party tools that can provide more robust signature management capabilities.

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References:

• Format your disclaimer
• Limitations of organization wide signatures