Thuderbird focus stealing

[William Murray]

   Hello all,
          I have a UI issue with thunderbird. When I reply to an email 
the next
thing I do is drag it into the corresponding 'dealt with email on that 
subject' folder
Maybe this is an unusual behaviour.
   The problem is that as I drag it a notification pops up in the bottom 
right
corner saying my mail is delivered, and it messes up the mouse focus. I
am still dragging, but I cannot drop. So I have to let go, go back to the
mail and pick it up again.
   Sounds trivial but it happens so often it gets frustrating.
     Any ideas how to avoid this?
       Thanks,
          Bill