Enable Preservation Lock on Retention Policy

Watch a YouTube video that walks you through the process:

Here is the code featured in the video:

Import-Module ExchangeOnlineManagement

Connect-IPPSSession -UserRPSSession:$false

Get-RetentionCompliancePolicy | Where-Object {$_.RestrictiveRetention -eq $True}

Set-RetentionCompliancePolicy -RestrictiveRetention $True -Identity "Preservation Lock Test"