Any email system you have "inbox , sent, archive, deleted..."
I don't how you structured internally your system but a good Idea
is if I open my "Inbox" (name it how you like) I must have by default a thread view by date. Each thread must include: Incoming email unread, read, deleted email (and not yet flushed), archived email. In short everything related to any thread.
And if course, displaying each status very clearly (maybe slanting the subject of archived, barring the subject of deleted ... etc... upto you or colours?).
I appreciated the quick correction of the bug of 2 letters extension files always misinterpreted as web links...
Sorry, this request is confusing. Please create reatures requests for each indivitual feature.