Starting April 4, 2016, 5-digit postal codes are required for all shipments to and from Korea
The Korea Postal code system changed from a 6-digit postal code system to a 5-digit postal code system on August 1, 2015. While FedEx internally converted its system to the 5-digit postal code, customers were asked to continue use of the old 6-digit system for shipments to and from Korea. FedEx would then convert the 6-digit postal codes to the 5-digit postal codes to facilitate smooth customs clearance.
The FedEx internal system is now calibrated for the 5-digit postal code, and starting April 4, 2016, the FedEx system will ONLY accept 5-digit postal codes on shipping documents for all shipments to and from Korea and in all FedEx shipping tools, including 'Get Rates & Transit Times' and 'Schedule and Manage Pickups' on fedex.com. On and after April 4, 2016, the old 6-digit postal code will not be accepted by the FedEx system.
You can use this tool to find the new postal code (although we suggest customers check with their customer to get the accurate code)
http://www.epost.go.kr/roadAreaCdEng.retrieveRdEngAreaCdList.comm