Idiot proof instructions to this arrow please :D
It is not at the top of the mail (where you could sort by size etc in outlook).
you can also "find" items with attachments in the search function, but there doesn't seem to be an option to sort them...
There is a button at the top left that looks like a little arrow, it sorts by read, unread, starred and unstarred, but otherwise I don't believe it sorts like outlook does.
HTH