Software does not offer an option to change font size. The suggestion I have is to zoom in and out with the browser with ‘ctrl and +/-’.
Mark Mail as Unread:
Click on the message you want to mark unread (It should be highlighted blue).
Click the ‘Mark’ button near the top menu >> ‘As Unread’.
Message Highlighting:
Go to ‘Setting’ in top right.
At the bottom of the preferences section is a section called ‘Message Highlights’ to filter based on whatever criteria you choose.
