Script to set every mailbox to use the default auditing settings from Microsoft

Convert-MailboxAudittoDefault.ps1

$mailboxes = Get-Mailbox -ResultSize Unlimited
$total = $mailboxes.Count
$count = 0
foreach($mailbox in $mailboxes){
	Write-Progress -Activity "Updating auditing: $($mailbox.UserPrincipalName) ($count or $total)" -PercentComplete ($count/$total*100)
	$count++
	Set-Mailbox -Identity $mailbox.ExternalDirectoryObjectId -DefaultAuditSet Owner, Admin, Delegate
}