Microsoft Outlook Classic Email Signatures Picture Display Issues

Hi, I also posted this to Microsoft. No response so far:

Description

We have identified a reproducible regression affecting multiple unrelated customer environments using Classic Outlook and Folder Redirection.

All affected environments have the following configuration in common:

• Classic Outlook for Windows
• %APPDATA% redirected through Group Policy to a UNC network path
• HTML email signatures stored under %APPDATA%\Microsoft\Signatures
• Signature images stored in the associated _files or localized _bestanden directory
• The signature HTML and local image files remain present and accessible
• Images are already missing when a new email draft is created, before the message is sent

The issue therefore occurs locally in the Outlook/Word editor and is unrelated to Exchange Online, SMTP transport, spam filtering, mail gateways, or the receiving mail client.

Affected builds reproduced

Office Professional Plus 2019 Volume/SPLA

• Affected build: 16.0.10417.20197
• Released: August 11, 2026

Office LTSC Professional Plus 2024 Volume

• Working build before update: 16.0.17932.20700
• Affected build after update: 16.0.17932.20910
• The issue appeared immediately after updating the same installation and user profile 

Reproduction steps

1. Configure Folder Redirection for AppData to a UNC path, for example \fileserver\profiles%username%\AppData\Roaming.
2. Configure an HTML signature in Classic Outlook containing one or more locally embedded PNG or JPG images.
3. Confirm that the HTML file and image files exist under %APPDATA%\Microsoft\Signatures.
4. Start Classic Outlook and create a new HTML email.
5. On the earlier Office build, the signature images are displayed.
6. Update Office LTSC 2024 to build 16.0.17932.20910, or Office 2019 Volume to build 16.0.10417.20197.
7. Start Classic Outlook and create a new HTML email.
8. The signature text is present, but the images are missing immediately in the draft.
9. Reinserting or recreating the images does not provide a persistent solution.

Additional technical observations

• Folder Redirection to a UNC path is common to all affected environments.
• The image files remain available on the UNC path.
• The HTML signature still contains references to the image files.
• Outlook may generate or use an RTF version without the images.
• The defect is visible before message submission.
• Internal and external recipients can receive messages without the images because the images were already absent during composition.
• Multiple independent customer environments show the same behavior.
• Reverting Office to an earlier build restores the expected behavior.
• Updating the same Office LTSC 2024 installation from 17932.20700 to 17932.20910 reproduces the issue.

Expected result

Classic Outlook should load and embed the signature images from the redirected %APPDATA%\Microsoft\Signatures directory when composing a new HTML email.

Actual result

The signature text is loaded, but the images are not displayed or embedded when the new message is created.

Requested action

Please reproduce this issue using AppData Folder Redirection to a UNC path and escalate it to the Office/Word engineering team. Please confirm whether this is a regression introduced by the August 11, 2026 Office security and quality updates and provide a corrected build or supported workaround.

A similar issue was previously documented by Microsoft, but the current August 2026 regression occurs on builds newer than the published fixed builds.

Additional technical findings

Microsoft Sysinternals Process Monitor confirms that OUTLOOK.EXE accesses the signature files directly through the UNC path configured by AppData Folder Redirection:

\server\redirected-folder...\AppData\Roaming\Microsoft\Signatures<signature>

When a new email message is created, Process Monitor records repeated CreateFile and ReadFile operations against the HTML signature file and its associated resource folder. During these operations, results including SHARING VIOLATION, NAME NOT FOUND, and END OF FILE are recorded.

The HTML signature file and its associated image files are present on the UNC path and are accessible to the affected user. Nevertheless, classic Outlook does not load or embed the images when creating a new email message.

The issue occurs locally during message composition, before the email is submitted or sent. Exchange, SMTP transport, mail filtering, and recipient-side image settings can therefore be excluded from the affected processing stage.

The same behaviour has been reproduced with:

• Microsoft Office Professional Plus 2019, build 16.0.10417.20197
• Microsoft Office LTSC Professional Plus 2021, build 16.0.14334.20848

Both affected builds were released as part of the Microsoft Office updates dated August 11, 2026. All affected environments identified so far use AppData Folder Redirection to a UNC path.

Based on these findings, the issue appears to be a regression in a shared Microsoft Office or Word component responsible for processing classic Outlook signature resources from a UNC-based redirected AppData location.

Attachments cannot be included with this submission. However, the complete Process Monitor trace and supporting screenshots are available and can be provided through an alternative secure upload method upon request.

Kind regards,

Michael van Zomeren.

@H4ppyUsers69! said

Email Signatures Picture Display Issues [in] Version 2607

Known bug. Only fix, as you have already determined, is to rollback to the previous version.
See: https://learn.microsoft.com/en-us/answers/questions/5977711/in-outlook-signiture-the-compani-logos-are-gone

when I rollback to an older channel. Microsoft is automatically updating itself. I've confirmed I've disabled "Auto Updates"

Did you use these instructions?
https://support.microsoft.com/en-us/office/lifecycle/how-to-revert-to-an-earlier-version-of-office

If not, which method did you use to pause MS 365 Updates?
https://learn.microsoft.com/en-us/microsoft-365-apps/updates/configure-update-settings-microsoft-365-apps

Is Microsoft plan on rolling out an formal update to resolve these issues?

There has been no official acknowledgement of this issue and no indication from Microsoft on when a fix will be release, that I am aware of.

I got Version 2608 Build 16.0.20326.20072 this week, but since I didn't have the bug in 2607 I can't test to see if it's fixed in 2608. You might want to let a few clients upgrade to 2608 and test. Please report back your findings so the rest of the people facing this issue can benefit.

I wrote a script to roll back the DLL on Outlook 2016 for single or network deployment unit Microsoft fixes it!

https://www.bleepingcomputer.com/forums/t/818373/outlook-2016-signatures-broken-shows-red-x-with-redirected-appdata/?p=5891625

Hi,

Thank you for your detailed sharing, and I'm truly sorry for the difficulties you have experienced.

Based on your description, Microsoft does have a support article for an earlier issue with the identical error message Images are not displayed in emails, newsletters, or signatures in classic Outlook | Microsoft Support, but that incident was attributed to the May 12, 2026 updates and is marked as fixed. The Current Channel release notes for Version 2608 only state “Various fixes to functionality and performance”, and there is no official article or documentation confirming that Builds 20228.20190 and 20326.20100 introduced this specific signature-image regression, as well as a published ETA for a corrective update.

Therefore, this could be a new regression or an environment-specific recurrence. Since rolling back to older channels helps resolve the situation, I highly recommend staying in the older channel and reporting this issue to Microsoft through Outlook > Help > Feedback so the engineering team can acknowledge and investigate it.

For your second concern, turning off Disable Updates is not necessarily authoritative in a managed business environment, as Microsoft 365 Apps updates can be controlled by several mechanisms like Group Policy, Microsoft Intune, Microsoft 365 Apps admin center Cloud Update, Office Deployment Tool configuration, etc.

Therefore, if Office updates again after you disable Auto Updates, the best next step I would suggest is to reach out to your company's IT department and ask for their help. They can help you check whether there is a Cloud Update configuration, Group Policy, or Intune that forces Office updates on your device.

Also, you can request your Global Administrator to open a support case with Microsoft regarding the image display issue in classic Outlook. A technical support engineer can initiate a remote session, assess backend configurations, and perform diagnostics. If necessary, they can escalate the matter to a specialized team for further investigation.

• For guidance on how to request support, please share this link with your admin: Get support - Microsoft 365 admin. 
• In case you do not know who your IT admin is, kindly refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support

Please note that, as an independent advisor, I do not have access to Microsoft's internal systems, diagnostic tools, or backend resources that would be required to investigate or resolve account-specific issues. However, I sincerely hope the information provided helps point you in the right direction and assists you in finding a resolution.

I hope you find this information useful. If you have any questions or need further support, please don’t hesitate to reach out at any time.

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