To submit your request at the airport, please deposit your envelope with receipts in a mailbox of the national postal service.
At Schiphol, Amsterdam airport you can use the orange mailboxes. There is an orange mailbox located opposite the customs desk.
All airports have a general postal office or mailboxes of the national postal service in various locations. To be sure, check the airport website or contact customer services a day before your departure. You can also ask an airport employee to point you in the right direction.
Don't forget to use an envelope, a postal stamp, your contact details and registration numbers.