What zone are Outlook attachments in?

If I wanted to target .zip Outlook attachments, which zone are they in under heuristics?
In my opinion, they should really have their own zone... I've raised a feature request in the business community, but I've posted this question in home since it applies to everyone.
 
Feature request:
https:///t5/Feature-Requests/Create-heuristic-zone-for-decompression-utilities/idi-p/56295