The June 3, 2015 announcement that Exchange Online would provide “new auto-expanding, highly scalable archiving. This allows you to take advantage of a truly bottomless archive…” naturally created a lot of customer interest, especially for Office 365 tenants who need to retain large amounts of email information for compliance purposes. Tenants who want to import legacy email in the form of user PSTs or extracts from legacy archive servers also anticipate the ability to store this data in archive mailboxes. Unfortunately, the anticipated rollout of expandable archives has not proceeded quite as smoothly as predicted... https://www.petri.com/exchange-bottomless-archives
