[German]Since the August 2026 updates were installed, several users have reported that something seems to have gone wrong with how images are displayed in Outlook Classic signatures. A red X now appears in place of the image. The collective wisdom of the blog's readership has confirmed that this bug is caused by GPO folder redirects.
On August 11, 2026, Microsoft released various security updates for Office applications still under support (see my German blog post Patchday: Microsoft Office Updates (11. August 2026)). There were also security updates for Outlook Classic (all versions), which are intended to address several RCE vulnerabilities (in Word).
Outlook classic: Images are missing
Shortly after August 2026 patchday German blog readers reporting issues with Outlook classic. Some users of Outlook Classic are reporting, that the August 2026 update is causing the issue, that images in their signatures are not shown anymore. Instead, only a "red X" is displayed.
Even if you manually reinsert them, they disappear again after saving. Outlook Classic. All Office versions are affected in some cases. I've mentioned that issue within my blog post August 2026 Patch Day Recap (Office, Windows).
GPO redirection is the culprit
German blog readers reported later, that affected users are having a folder redirection of %appdata% via GPO. The error occurs only when folder redirection is active and a UNC path has been defined for AppData. If you change the path to an absolute path, everything works fine again. Details may be found within my German blog post [use build-in translator to read the blog post in English].
Hello,
The problem is not folder redirection, the problem is that someone in Redmont does not understand fodler redirection anymore.
Roel Niesen
You can embed the images into the signature's .htm file in base64. I created a small Powershell script using ChatGPT and tested successfully. However, if you try editing the signature, Outlook or Word will convert the embedded images to files again.
Hello,
Yes, but when you change the signature, the problem is back.
Also remove the signatuers and sync them back from O365 will work until you change something.
I wrote a rollback script to push out via group policy to fix Outlook 2016
https://www.bleepingcomputer.com/forums/t/818373/outlook-2016-signatures-broken-shows-red-x-with-redirected-appdata/
Thanks
I ended up editing the htm file and replace the first <html … > tag to simply <html>. Images are displayed but when you use word or signature editor and save after a modification then you have to modify the tag again.
9/1/2026 Patch Tuesday version 16.0.5569.1003 has re-broke Signatures and also broke Cut and Paste, including drag function to copy formulas
Latest Rollback Scripts
https://www.dropbox.com/scl/fi/mkyj7bomgw0ipnpkg3lb5/xlsFix.zip?rlkey=n2zoa0088cbg1yvn0v94guqbs&st=wkv1hp73&dl=0
and
https://www.dropbox.com/scl/fi/xbu3ad0cutpx9lgmymc64/msofix.zip?rlkey=2noq59jpkbamk39y3r0xlxy3m&st=lk1pbao2&dl=0
see
https://www.bleepingcomputer.com/forums/t/818373/outlook-2016-signatures-broken-shows-red-x-with-redirected-appdata/
Thanks, got similar reports from German readers.