Why I cannot maximize the outlook message windows…

Hi everyone

Usually for out look whenever we click on the messages a new window will pop up in maximized view whereas in Mac book air 2020 outlook application it is not available.

Inbuilt email in Mac this option is available , my concern is with outlook application which we download from AppStore

Is there any option to make the messages in full screen ,if it is available, can anyone advise how …?

regard

syam