We have on-premise Exchange servers in a DAG, and presently have three backup jobs related to Exchange and Active Directory.
Backup #1 gets the Microsoft Information Store on one of the Exchange servers. This job gets all the Databases and Logs.
Backup #2 is a Simplified Disaster Recovery backup of the Domain Controller, which includes drives, System State and Active Directory.
Backup #3 is a Simplified Disaster Recovery backup of the Exchange Server, which includes the Drives and System State, but not the Microsoft Information Store.
Do I need the third backup job? Would I ever need to restore something from the flat files or System State of the Exchange Server?