1. First you need to go to the settings in outlook on web, which you can do by clicking the cog icon in the top right. 
  3. In the search box at the top of the settings type in Message Format and then click Message Format in the list.
  5. This will open a panel will a lot of options, the one we are looking for in that section is Always show From click the checkbox
  7.  When you have checked the box make sure to save the changes at the bottom and click the cross at the top right of that window.