A management request came in to report email sent by some users to external recipients. Although you might not agree that this is the right thing for any organization to do, it’s very possible by exploiting the message trace information retained by Exchange Online for 90 days. As a bonus, we email the report generated from message tracing data to the requesting manager. Isn’t PowerShell just wonderful?
https://office365itpros.com/2022/04/13/message-tracing-email-activity/
