The postal network is an interconnection network that possesses many desirable properties which are important in network design and applications. It includes hypercubes and Fibonacci cubes as its special cases. The postal network can also be considered as a flexible version of the hypercube which relaxes the restriction on the number of nodes and thus makes it possible to construct multicomputers with arbitrary sizes. Basically, the postal network forms a series (with series number ) that is based on the sequence Nn = Nn , 1 + Nn , , where n is the dimension and Nn represents the number of nodes in an n-dimensional postal network in series . In this paper, we study topological properties of postal networks and relationships between different postal networks. One application of postal networks is also shown in implementing barrier synchronization using a special spanning tree called a postal tree.