425900。 The postcode of Dong 'an County, Yongzhou City, Hunan Province is 425900. The first two digits 42 represent provinces, municipalities and autonomous regions, the third digit 5 represents postal areas, the fourth digit 9 represents counties and cities, and the last two digits 00 represent specific delivery areas. When filling in the postal code, we should pay attention to determining the province, city, district and other information of the mailing address to ensure that the postal code used is correct in the region.