Outlook The opening window display size

Hi I'm getting older and find it difficult to read the screen in Microsoft Outlook where all the emails are displayed. This is not about the emails themselves - it's the window which shows all the emails, choose the email account and has the ribbons at the top. How do I make either the font size bigger or the window bigger - zoom and zooming using the mouse doesn't work.   Thanks.

PS Got new glasses - bifocals - and that's not helping LOL