Perhaps a nit-picky item however when I create new mail folders, the field you type the name into isn't focused automatically.
Most UI/UX auto-focuses fields so that natural workflow is kept intact and typing doesn't cause the page to react in a weird way.
I'm sure there are instances all over the UI where this could be applied but new folders in mail is where it drives me bonkers on a daily basis.
Please and thank you =)