Mail.app will only sort by Unread I have a weird problem with Mail.app (7.3) on mavericks (10.9.4) where every folder is now set to 'sort by unread' 

I can change the sort order while I'm in the folder, but if I leave, and return to that folder.. it switches back to 'sort by unread' again.

I can't find any way to change this permanently, and I certainly didn't configure it this way.  Does anyone have any clue why it's doing this?

Info:
There are two accounts configured,  one Exchange (work) and one IMAP (not work)
Usually that is done in 

Mail-View-Sort by: select your choice (see if sort by unread is checked)

If your selection does not stick (remain) the try repairing the permissions using the Disk utility.