Hi @David Seikis ,
Is this a problem that has only recently occurred on all of these three machines? Can everything work fine before? If so, please check what specific operations users did before this problem occurred.
The problem occurs after dragging and dropping a PDF file from other mail into a concept mail (new e-mail)
Does this issue only occur to the specific format(.pdf) files? Can this issue be reproduced if users drag and drop other files such as .doc and .xls from other mail into a concept mail?
Also, what if users drag and drop pdf files from desktop into a new e-mail?
I also tested a lot in my Outlook (Microsoft Office Standard 2016 16.0.4266.1001) but could not reproduce this issue as well. Since you have already tried repairing or reinstalling Office, it should be able to exclude most factors which related to Outlook client. There could be some add-ins in your Outlook client that might cause this issue, so it is suggested to start your Outlook in safe mode (Press Win + R, type “outlook /safe”, press Enter.) and see if the issue has any difference.
Besides, corrupted registry keys may also lead Outlook issues. Please try the steps below to remove your Outlook registry completely and see if it works:
- Exit Outlook and open the Registry Editor
- Navigate to: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0
- Right-click the Outlook folder
- Rename it as Outlook1
- Restart your Outlook and add your email account to test
(Note: Serious problems can occur if you modify the registry incorrectly. Before making changes, back up the registry to restore it in case something goes wrong.)
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