So, that's the top level. The 2nd level would be more analogous to individual email threads within those groups.
Once you get down to the individual conversation level, the fine-grained management bits you talk about are not good UX, they're band-aids for dealing with bad UX.
Well, whether they’re good or bad UX depends on assumptions about whether the second-level categorization is more meaningful organization-wide or on a user-by-user basis.
Once you get down to the individual conversation level, the fine-grained management bits you talk about are not good UX, they're band-aids for dealing with bad UX.