After the capitulation of German Reich, several areas under Soviet occupation were given permission to issue stamps. Those provinces were:

Berlin-Brandenburg:

 

Mecklenburg-Vorpommern (Mecklenburg-Western Pomerania):

 

Ost-Sachsen (East Saxony):

 

Provinz Sachsen (Saxony):

 

 

Thuringen (Thuringia):

 

West-Sachsen (Western Saxony):


 

 

In 1946 they were replaced by general issues for Anglo-American and Soviet zone.
In 1948 purpose-printed stamps for whole Russian Zone were issued. Here are some of them:

 

And on October 10th, 1949 German Democratic Republic (East Germany) was proclaimed.
To see some early GDR stamps click here.