In Outlook, Click File > Options, and then click the “Add-Ins” category on the left.

The Add-ins option

This will open the Add-ins section. To enable or disable add-ins, make sure that “COM Add-ins” is selected in the dropdown (it’s the default, so you shouldn’t need to change it) and then click “Go.”

The Go button for managing add-ins

This opens up the COM Add-ins dialogue, where you can enable or disable add-ins.

The COM Add-ins dialogue

Enabling and disabling is a tick-box exercise—a tick means the add-in is enabled; no tick means the add-in is disabled. To disable an add-in, untick it and then click “OK.”

The COM Add-ins dialogue with an add-in and the OK button highlighted

Important: Make sure that you don’t click “Remove.” This will uninstall the selected add-in, not disable it!

When you go back into File > Options > Add-ins, the add-in you disabled will be visible in the disabled add-ins section.

The Add-ins option showing a disabled add-in

The add-in will remain disabled until you enable it again. Test to see if your problem occurs when the add-in is disabled; if it does, keep disabling your add-ins one by one until you find the culprit.