COM and VSTO add-ins aren't supported in the https://learn.microsoft.com/en-us/office/dev/add-ins/outlook/one-outlook : The new Outlook on Windows aims to unify the extensibility experience acros...
Yes, in cybersecurity and spam control, we require the users to manage possible spam using the add-in button available in the usual desktop app. Still, it's painful to request the users to do all the current processes to add it to the new outlook. For admin and GPO this feature should be mandatory...