The site lists on their Terminal page that a drop box is “outside across from the Airline Ticketing Area.”
Check out Paradies, which may be the second floor gift shop pre-security.
Robert wrote in (and sent a postcard!). He mentions the drop box is curbside in front of Departures.
On Google Maps, the drop box is located in the median refuge by departures.
Last updated 19 August 2018