Selected Exchange Online service plans and licenses include an Online Archive for a mailbox. Microsoft describes which licenses include which options.
After activation, the Online Archive for an account is now also available in Outlook Mobile.
Users should keep in mind, an Online Archive is different than the Archive folder in Outlook.
Archive folder
A local archive that stores older emails directly in the user’s mailbox. Using the Archive button to move messages to the Archive folder doesn’t reduce your mailbox size. All accounts have access to an Archive folder.
For Microsoft 365, Outlook.com, and Exchange accounts, the Archive folder is one of Outlook’s default folders, like Inbox, Sent Items, and the Deleted Items folder. This folder can’t be deleted.
Online Archive
An archive mailbox is a specialized mailbox that appears alongside the users’ primary mailbox folders in Outlook or Outlook on the web. Users can access the archive in the same way that they access their primary mailboxes. In addition, they can search both their archives and primary mailboxes.
The Online Archive for an account is listed in a new section in Outlook Mobile.