not sure what you mean "headings", click on view>layout and make sure that "show preview" is un-ticked, click on apply, that will get rid of the preview pane which is generally regarded as un-wanted, this will leave your inbox full screen.
Alienware 17 R4 2017 review
Interview: Camille Walala on her giant 3D installation inspired by childhood funfair visits
Best iPad buying guide 2017
Où regarder le British Open 2017 ?