From 01-01-2022 and onwards it will not be possible to ship to Belgium with an EDI/FTP connection (Zelfbouw). Please implement Belgium shipments via the API.
For further information about Belgium products in the API please take a look at the API page in the menu on the left. Further documentation for Belgium products implementation can be found here.
For incidental shipments to the Belgium you can also choose to use the Mijn PostNL environment. You probably already have an existing account or you create a new account via Mijn PostNL.