Need an automated reminder about emails that have not been responded to

Hi, I have an employee that keeps missing emails in his inbox. this is a PROBLEM! My other job has some automated reminder (bumps to top of inbox, says :Received X days ago, reply?) when I dont repond to an email. (See screenshot). He is a great employee otherwise but we are losing jobs over this! Any other ideas for keeping him from forgetting to respond are welcome. 

How do I set this up for Microsoft365?