MS Office 2016 error popup

I have a couple of PCs that are issuing an error popup when a user opens Outlook. The popup can be reproduced at will by closing and opening Outlook each time. This happens for all users on the particular PC.

error message

  • Run an Online Repair of MS Office
  • Uninstall/reinstall of MS Office 2016 (O365)
  • Run dism
  • Run sfc
  • Run in safemode
  • Disable Addons

I am not seeing any errors pertaining to this in the Event Viewer. This popup doesn't seem to hinder the ability to use Outlook - mail can still be sent and received. This seems to be more of an annoyance than anything because after clicking OK, Outlook performs as normal.

PC Spec
Dell 7040
Windows 10 Pro x64
MS Office 2016 (O365 Business Retail x86)
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Reece DoddsCommented:
It seems to be related to a software called Add-In Express (
I'd suggest looking for that software in the Programs and Features and either reinstalling or uninstalling.
If you can't locate it, do a search in the registry for 'AddInExpress.MSO.2005' and delete any entries pertaining to it.  Note that you should always backup before making any registry changes as you can damage the OS configuration and make the system unbootable.

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Member_2_6375190Author Commented:
The one thing I did not try was looking in regedit. I appreciate your help and I have found the problem clear as day just as you have stated.
Member_2_6375190Author Commented:
Thank you.
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