Comment 7 for bug 120672

Perhaps the action associated with such a context menu can include bug 195605.

That bug states that right now when Junk is deleted [either "automatically after
xx days "or via delete] the junk messages aren't deleted but go to TRASH.

So pressing EMPTY JUNK in a context menu basically should be a
1) "MOVE JUNK TO TRASH" [which needs to be followed by an "EMPTY TRASH"]
2) "EMPTY JUNK" which removes junk directly