Occasionally I'm asked at work to delete an email that has been accidentally sent out to the wrong people. It doesn't happen very often, but inevitably when it does happen, I forget the process, so I am including it here for personal reference.
Create a content search rule within the Microsoft 365 Compliance area - https://compliance.microsoft.com/homepage (take note of the name you call it - you'll need it in the New-ComplianceSearchAction command.
Run Powershell as administrator and enter the following commands...
set-executionpolicy remotesigned
(only use this if you get an error about not being able to run scripts via Powershell)
$UserCredential = Get-Credential
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://ps.compliance.protection.outlook.com/powershell-liveid/ -Credential $UserCredential -Authentication Basic -AllowRedirection
Import-PSSession $Session
New-ComplianceSearchAction -SearchName "Rule Name used in content search" -Purge -PurgeType SoftDelete
If you would like to see the progress of the search, use the following command.
Get-ComplianceSearchAction