Hello,

Yes there is! You can get this information by using the SMTP Logs. Login as System Admin, Go to Troubleshooting on the left. In the Options tab find SMTP In protocol logging, set that to Detailed.

Wait for the user to send their mail.

Now you can check the log, same area but in the View Logs tab you can search the SMTP logs for
Authenticating as <the email address of the user>
This will return the Time, Session ID, and their IP.