Hi DJ. In Ireland, VAT is not applicable to goods exported outside the EU nor is VAT applicable to the the associated costs of those exports. This includes postage, trucking, courier, airfreight, ocean freight, brokerage costs etc.
Conversely on imports all those costs together with the actual invoiced value of the goods are taken together to establish the "Landed Cost" which is the figure on which VAT and Duties are applicable.
Yes in effect they are applying vat on foreign postage but on the basis that it contributed to the cost of the goods.