The most interesting part of Polish Postal History is the time between Poland’s independence and the first official stamps..
The accepted date of the independence of Poland, after World War 1, is the 11th November 1918. This date, however, really only applies to the central part of Poland occupied by Germany (General-government Warshau). They freed the area occupied by Austria on 29th October 1918. The Germans held the Wielkopolska area till 27th December 1918 and the Pomorze area till 10th February 1919. During this time, local areas and towns issue local postage stamps until the first issues of Poland could be used. For more information, please check out this site on Polish postal history.