To make inplacearchives available to users, they must satisfy the following criteria:
Be assigned a suitable licensing level within Office365 (typically Office365E3/E4 or equivalent, ExchangeOnline Plan 2, or as an add-on with other plans).
Have the feature enabled by using Office365admincenter or PowerShell.
Be using a supported mail client (either Outlook2013, Outlook2010, OutlookWebApp and certain versions of Outlook2007).