Message trace is a tool used to investigate and analyze the flow of email messages within an organization. It provides detailed insights into the path a message takes, from the sender to the recipient, helping administrators identify issues or delays in email delivery.
1.Log into EAC Exchange Admin Center
2. Under Mail-flow click on 'Message trace' 
3. When in the Message trace tab click 'start to trace'
4. Type in the sender & recipient address and place the right date & time 
5. The the next page will show you the search results to investigate mail flow.
