It is different not sure how to explain it. All my spam or junk mail goes to a folder called balk mail. That is for yahoo accounts. I just removed that account. Having to delete each one at a time was getting to me. Every thing that wasn't from people I know or Microsoft related I marked as spam.
I think the new "mail" app is caught in the development cycle and is missing some features right now.
Not as bad as the new "people" app but still, a work in progress.
Although it's a relatively simple task to open your Trash folder, select the top most item and then just click the hell out of the "delete" item near the top right, of what I'll call for lack of a better term the menu bar, until they're all gone.