If the window is opening minimized then the restore up button should work but if it doesn't try maximizing the window then resizing it down to the size you want.  This size should then stick.  The main Pegasus Mail window may need to be windowed and not maximized in order to do this. 

If the window is shrunk to a minimized size (no 'restore up' button), then you should be able to grab the top right corner and stretch it back to size.

Starting about 3 weeks ago whenever a new window is opened (send new mail, reply, etc.) in Pegasus

the window is minimized in the bottom left corner. It can be maximized, but not partially so. Previously

new windows were opened part-way and the position in the mail window was adjustable and remained

between sessions. I must have done something inadvertently -- but what??