Mailbox Delegation question

All roads lead to Rome, but you want to check the set of permissions per mailbox, not the whole population. Then you can filter if that set contains a FullAccess for specified user. If there are results, the delegation exists, if not then not. Also, you might want to leave the inherited permissions out, resulting in something like (for readability, I didn't turn it into a one-liner :) ):

$account= 'special.svc@mydomain.org'
Get-Mailbox -ResultSize Unlimited | ForEach-Object {
$Object = [PSCustomObject]@{
Name= $_.Identity
DelegationFound= [bool]( Get-MailboxPermission $_.Identity -User $account | Where {$_.AccessRights -contains 'FullAccess' -and -not $_.IsInherited})
}
Write-Output $Object
}