Auto-Expanding Archive (Exchange Plan 2)
A full guide to this process can be found here - https://learn.microsoft.com/en-us/purview/enable-autoexpanding-archiving
USER MUST HAVE EXCHANGE ONLINE PLAN 2 LICENCE BEFORE COMPLETING THESE STEPS
The steps have to be done in order or this won't work
Most clients have predefined retention policy's but if you need to create a new one, follow this guide: https://learn.microsoft.com/en-us/exchange/security-and-compliance/messaging-records-management/create-a-retention-policy
STEPS TO COMPLETECOMP
Step 1: - Head to office 365 admin tenant & access Exchange Admin Centre
Step 2: Turn on In-Place Archive for the affected user and call it "(User's name) Archive" (This is under Mailbox in the user settings in exchange)
Step 3: Open Powershell and run - Connect-ExchangeOnline then log in with appropriate 365 tenant admin account
If you can't run Connect-ExchangeOnline - try these:
https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.security/set-executionpolicy?view=powershell-7.5 (set execution policy unrestricted)
https://learn.microsoft.com/en-us/powershell/exchange/connect-to-exchange-online-powershell?view=exchange-ps (Import exchange module)
Step 4: Once logged in, run the command Enable-Mailbox "User Email Address" -autoexpandingarchive
Step 5: Confirm with the user how long they want before archiving takes place (typically 2 years, will need to create a new retention policy for longer)