Create an Office 365 plan for Exchange Online. The Office 365 plan specifies which messages are archived, how long they are retained, and which messages are content indexed.
You will assign the Office 365 plan to the mailboxes that you add to the Exchange Online app.
If some mailboxes have different archiving requirements, you can create additional Office 365 plans for Exchange Online.
From the navigation pane, go to Manage > Plans.
The Plans page appears.
In the upper-right area of the page, click Create plan, and then select Office 365.
The Create Office 365 plan dialog box appears.
In the Plan name box, enter a name for the plan.
To enable archiving on the mailbox, move the Enable backup on archived mailbox toggle key to the right.
Under Retention settings, specify how long to retain the data:
To retain for an unlimited time, select Retain indefinitely.
To retain for a limited time, select Retain deleted items for, and then specify the amount of time.
Retention settings is recommended if you back up the data. Retention settings applies to both Exchange Online and Exchange on-premises configurations that use Exchange Web Services.
Under Search settings, specify the types of data to include in searches:
To include the bodies of emails and attachments, move the Content search toggle key to the right.
If you include the bodies of emails and attachments, to see previews of messages while browsing, do the following:
Move the Pre-generate previews toggle key to the right.
In the Preview storage location box, enter the UNC path for the network location where you want to store the preview files.
Enter the user name and password of a service account that has write access to the network location.
To include personally identifiable information (PII), such as Social Security numbers and credit card numbers, do the following:
Move the Entity search toggle key to the right.
Select the entities to include in searches.
Only the entities that you select are detected for end-user data requests and projects that use this plan.