Hi @Tee356 ,
Welcome! As I know, DXperience is not Microsoft product and we do know little about that.
Does this pop-up issue only happen to specific Outlook client on specific devices? Or will happen to all the users on different devices?
If this only happen to specific devices, as @Geoff Whalley mentioned above, it is suggested to check if users has installed some third-party add-ins or third-party programs on these devices. Please try checking the Task Manager and Programs and Features in your windows, compare with other devices which can work fine and see if there is any difference. Starting your Windows in safe mode and running Outlook client alone can also help test about it. By the way, in order to make sure that your Outlook client is fine, completely repairing your Office, creating and using a new Outlook profile is also a necessary procedure.
If this issue happen to all the users on different devices, sounds like it is more like global settings within your organization, please try to contact your administrator and check if they have updated specific configurations or programs recently.
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