Changing the height & width with Mail 2 appearance check

Hi,
Why is it impossible to change the width an height of the workspace when mail 2.0 appearance is checked (in the preference panel)? The little dot disapears so one can’t change the height and width anymore. I ‘m a bit of a windows’ manipulator ; if a text catch my attention, i change the size of the window to let it appear larger…

Thks
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