Exchange Online Archiving

Exchange Online Archiving is a Microsoft-hosted service that archives mailboxes from Exchange Online or Exchange Server.

Capabilities and Limitations

Exchange Online Archiving maintains a parallel mailbox (called the archive mailbox) for items archived from a user or shared primary mailbox. This feature limits primary mailbox size and helps centrally enforce organizational policy for mail and related content. Users can view and search their archive mailboxes, while organizations can enforce retention policies and legal holds and perform eDiscovery searches on archived content.

The separate Office 365 Import Service allows the import of existing on-premises archives to Exchange Online Archiving via direct upload of e-mail personal store (PST) files to Microsoft servers or shipping the data to Microsoft on physical disks, to speed initial migration of mailboxes from on-premises.

By default, the maximum size of the archive mailbox matches the maximum size of the primary mailbox being archived. However, customers can auto-expand archive mailboxes, adding storage without manual steps or Microsoft support calls. Capacity increases automatically when the archive mailbox size approaches its maximum. However, there can be a delay of up to 30 days before an increase becomes effective. Auto-expanding an archive mailbox can also restructure folders and affects some capabilities, such as search.