Display full FROM email address in Outlook
I think you could try adding a custom form configuration file in the following guidance to your client so that there will be a column displaying the sender's email address in the message list:
Show sender’s e-mail address as a column in the Message List
My test result in the following screenshot is for your reference:
If the sender's email address is a bit long, you could change the Reading Pane to bottom:
Besides, if you want to block the emails from the phishing sender, you could create an inbox or transport rule:
