After you create the Exchange app, you must associate public folders with the app.
To protect all public folders, you must enable the All Public Folders group, and then assign the Exchange plan to the group.
Before You Begin
Create the Exchange plan.
Configure the Exchange Online app.
From the navigation pane, go to Protect > Applications > Exchange.
The Exchange page appears.
Click the Exchange app that contains the public folders for association.
On the Content tab, select All Public Folders check box , click the Action button and then click Manage > Change plan.
The Edit association dialog box appears.
Select a plan, and then click Save.
Select All Public Folders check box , click the Action button , and then click Archive.
A message prompts you to confirm submission of the archive job.
To view associated All Public Folders, on the Exchange page, in the row of the app, click the Action button , and then click Restore.