If you want to delivery a parcel, you have two options:
Use a RFID tag
Input secret code
Either you scan a RFID tag or you enter a code, after some time you will see a green light flashing if the validation went well. So, then, you have 4 seconds to open the parcels compartment as it will stay unlocked for 4 seconds and then locks again.
Properly closing the door after delivery is strongly advisable.
Front door doesn't close by itself and it is good not to leave it hanging.
How To Deliver
In order to deliver a letter, you don't need any kind of validation or verification.
You just push the small front door of it, drop your letter and leave.