What is out for delivery then arrived at post office?

"Out for delivery" means that the package has left the post office and is on its way to the recipient's address. The package is assigned to a delivery driver who will deliver it along their daily route.

"Arrived at post office" means that the package has been delivered to the recipient's local post office and is ready for pickup or further delivery. The package will be sorted and processed by postal workers and either delivered to the recipient's address or available for pickup at the post office, depending on the delivery method and instructions provided by the sender.