To enable an inactive add-in that keeps unloading on restart in Outlook you should follow these steps:
First shut down Outlook, then uninstall the software providing the add-in from your machine.
Then go into regedit whilst logged in as the affected user and go to the following location:
Delete the REG_BINARY keys found in DisabledItems and CrashingAddinList folders:
Then navigate to this location:
Then delete the key (folder) that references the add-in (we are using Mimecast as our example below):
Reinstall the software that provided the add-in and then restart Outlook. The add-in should now load.
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