Before running the first backup operation, assign content to the default subclient.
Procedure
- 
From the navigation pane, go to Protect > Exchange.
The Exchange page appears.
 - 
Click an Exchange database.
The Exchange Database page appears.
 - 
In the Subclient section, click default.
The default page appears.
 - 
In the Content section, click Edit.
The Subclient content dialog box appears.
 - 
Select the databases that you want to assign to the default subclient, and then click Save.
 
What to Do Next
Specify the backup source for the default subclient.