As Admin you can delete specific wrongly send emails from your users mailbox : Open Exchange Powershell , To delete from user@example.com email with the subject “Mail delivery failed: returning
How to change exchange Preferred Server For DBHow to change exchange Preferred Server For DB
Open exchange Powershell Set-MailboxDatabaseCopy -identity {Database_Name\New_Server_Name} -ActivationPreference 1 Confirm: Get-MailboxDatabase 'Database_Name'|fl server, databaseCopies, activationPreference
How to delete exchange log fileHow to delete exchange log file
If you need to delete exchange log file in case of space problem or some other reason, Best do it safely -> open Powershell as Administrator and run : forfiles