Exchange IIS Logs data collection is failing with Unable to write to the data storage engine service.
Remove the duplicate UPN
The following powerhsell command should return all users with the UPN in question.
Get-ADObject -LDAPFilter '(userPrincipalName=*user@Domain.com*))'
If you have multiple domains in you forest you will need to run the command in each domain.
Once you identify the object with the duplicate UPN modify the UPN so it does not conflict.