[O365] Purge Deleted Users and Mailboxes from Office 365

Single­User Deletion:

Remove-MsolUser -UserPrincipalName username@mydomain.com

Get-MsolUser -ReturnDeletedUsers | Remove-MsolUser -RemoveFromRecycleBin -Force

Bulk User Deletion:

Get-MsolUser -MaxResults 30 -ReturnDeletedUsers | Remove-MsolUser -RemoveFromRecycleBin -Force