How to get Outlook signatures to use the current banner image on the server rather than the cached version

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How to get Outlook signatures to use the current banner image on the server rather than the cached version

Andrew Talbot 0

We've got 20 users using Outlook signatures which link to a banner image on the server (eg abc.com/banner.png), this is so we can update the image and show a new banner several times per year. Unfortunately Outlook will always serve the cached image rather than the current image. It's impractical to change the image link in every signature every time we update it, how can we fix this please?

We're using the Classic Outlook for Microsoft 365

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Answer 1

Michelle-N 14,470 Microsoft External Staff Moderator

Hi @Andrew Talbot

I understand that you have 20 users on Classic Outlook for Microsoft 365 using an email signature that includes a banner image linked directly from your server. When you replace the image file on your server to reflect a new banner, Outlook continues to display the previously cached image instead of downloading the new one. You are looking for a solution to force the updated image to display without needing to manually change the URL in every user's signature.

This step helps us understand the server-side environment. Could you please describe in more detail exactly where this image is stored? Furthermore, what is your exact process for updating the image (for example, overwriting the file via FTP, updating it through a web portal, etc.)?

To isolate the behavior, I conducted a test in my own environment. I hosted an image on OneDrive, inserted it into an Outlook signature (adding both the image and the link), and then edited and cropped the image directly within OneDrive. Upon checking Outlook, it did not automatically sync the newly cropped image. I found that I needed to manually navigate into the signature settings and save it again to force the client to fetch the latest version.

This step checks for environmental variables. Because I do not have full visibility into your specific network or hosting setup, comparing my test results with your exact workflow will help us determine the best path forward. It will help us identify if we need to adjust something on the server side or if we need to look at a client-side deployment script.

Please reply with the additional details regarding where the image is stored and how it is updated. Thank you for your understanding.

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Andrew Talbot 0 Reputation points

2026-03-17T13:53:37.0366667+00:00

Hi Michelle,

Thank you for your response. We store the company logo, accreditations logos and banner in a directory on the client's website hosting (eg abc.com/assets/banner.png). The logos stay the same, but the banner is intended to change every couple of months to deliver a new message, promotion etc. We upload the banners via FTP, keeping the same filename so we don't have to change the img path in the signatures, however Outlook continues to serve the cached version of the previous image/banner indefinitely.

The simplest option would be to prevent Outlook serving cached images in the signature, or even to clear Outlook's cache each time the banner is updated. This would be less troublsome than updating the image link every time on every user's computer.

Best regards

Andrew
Michelle-N 14,470 Reputation points Microsoft External Staff Moderator

2026-03-17T14:17:10.62+00:00

Hi @Andrew Talbot

Thanks for the update.

After further research and consideration, due to the limitations of the current environment, the best approach in this case would be for you to create a ticket in the Admin Center, as shown in the screenshot I shared below.

This will allow the issue to be escalated to a more specialized team who can provide deeper and more appropriate support. Thank you for your understanding.
Andrew Talbot 0 Reputation points

2026-03-17T14:45:20.4166667+00:00
Hi Michelle,

I've done that and had a very quick AI generated response back (pasted below) which doesn't address the issue at all:

Hi Andrew,

Thank you for contacting Microsoft support. I'll be working with you on your issue.

Summary of your issue: Based on our understanding of your issue, we're including some steps we believe will help troubleshoot your issue or provide more insights to help us resolve your request faster.

Insert the banner into the signature using the Image button: open Outlook Settings (or File > Options > Mail > Signatures in classic Outlook), choose the signature to edit, click the Image button, locate and insert the banner file, then save the signature. Use the Picture/Size options to resize if needed. [2]

Avoid VML-based or hand-edited HTML/VML in the signature because VML tags can make images appear as attachments instead of inline; use the signature editor’s image insert instead of pasting VML HTML. [2]

If Outlook shows a red X or fails to download an HTTPS-linked image, disable the Internet Options setting “Do not save encrypted pages to disk”: exit Outlook, open Internet Options > Advanced, under Security uncheck that option, click OK, then restart Outlook. This setting can prevent HTTPS-linked images from being downloaded/displayed. [1]

The retrieved articles do not include guidance for forcing Outlook to refresh or clear cached linked images (for example, programmatic cache clearing or cache‑busting techniques); because that information is not present in the provided docs, I can’t provide steps from these sources for forcing a refresh of already-cached signature images.

Sources from links listed in steps above

HTTPS linked images in HTML emails display the red X - Outlook | Microsoft Learn

Create, add, or change an email signature in Outlook - Microsoft Support

If you have questions or concerns about the steps provided, our understanding of the issue, or what we're asking for please let us know.

Once you are able to confirm the requested information, we can move forward with your issue.

Thanks again,

Microsoft Support

Your support request number is [Moderator note: personal info removed] if you need it.
Michelle-N 14,470 Reputation points Microsoft External Staff Moderator

2026-03-18T07:53:22.3266667+00:00

Hi @Andrew Talbot

Thank you for the update. I’ve sent you a private message, so we can continue our discussion there.
Andrew Talbot 0 Reputation points

2026-04-07T07:41:18.78+00:00

Good morning @Michelle-N , after 2 weeks support have finally finished revewing the support request, the response is below. They have basically just confirmed the outline of my original request, without offering any solution:

Dear Andrew,

Thank you for your patience while we reviewed the Outlook signature banner image behavior with our internal team.

We can confirm that this behavior is default Outlook functionality. When an image is linked in an Outlook email signature (for example, a banner hosted on a server), Outlook caches the image locally. Once cached, Outlook continues to display that version of the image and does not automatically refresh it, even when the image is updated at the original server location.

Because of this design, There is little that can be done on my end, I will be proceeding to archive this request.

Sincere apologies for the inconvenience.

Warm Regards
Michelle-N 14,470 Reputation points Microsoft External Staff Moderator

2026-04-07T11:39:00.8533333+00:00

Hi @Andrew Talbot

Thank you for your update. Based on the information you provided, this behavior aligns with what I initially tested in my own environment. In this case, it does appear to be considered default Outlook behavior.

Given this, the best course of action would be to submit a feature request directly through the Outlook Feedback Portal. This is a critical platform where Microsoft actively listens to user feedback. If an idea receives a significant number of votes and strong community support, Microsoft is more likely to prioritize its review and potential implementation. I strongly encourage you to upvote similar proposals there if you haven’t already.

Once you’ve submitted the feedback, feel free to share the link here. I (and other community members) would be happy to vote for it to help increase its visibility and priority.

Thank you for your understanding.
Andrew Talbot 0 Reputation points

2026-04-09T07:35:20.4166667+00:00

Thanks @michelle-N, I've done that and the link is: https://feedbackportal.microsoft.com/feedback/idea/14c6a28d-e633-f111-9a91-000d3a05c4f5
Michelle-N 14,470 Reputation points Microsoft External Staff Moderator

2026-04-09T13:49:13.0066667+00:00

Hi @Andrew Talbot

Thank you for your update. I hope this request will be considered soon.

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How to get Outlook signatures to use the current banner image on the server rather than the cached version

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