Get the Current Position of a Keyboard Maestro Palette

Yes it is.

My guess is your palette hasn't been displayed yet, after activating Mail. Try putting a delay in, although I'm not sure how to do that in AppleScript. You could activate it in KM and use a KM pause, then run your AppleScript, and see if that's what's wrong.

Ultimately you can trigger your macro when Mail becomes active - the palette will have been displayed by then (I think).

Also, have you seen:

If you download the action (you don't need to install it unless you want to), unzip it and look in the script file, it has all sorts of AppleScript window position stuff in it.