There is plenty of wasted space in Outlook GUI, but placing a live SEARCH field in the middle of the window title bar defeats the purpose of having something to move, select, or drag the window with. If the user has multiple windows open, the title bar gets more narrow and having the SEARCH feature fill that space makes it difficult to 'grab' the window to move it or to dock it to one side of the screen. Word, Excel, and other Office apps have the ability to collapse this; provide the same for Outlook.