Anyway, Sovdepia was without postal connections to foreign countries from the beginning of 1919 until mid-1920. This is a really remarkable fact - very rarely in modern history has a country totally lost mail links to other countries.
When mail services to abroad resumed in June 1920, then according to the Tariff of 7 June 1920 ordinary letters could be sent Free and Registered letters were charged at 10 roubles. A new Tariff of 30 September 1920 abolished all the remaining Free post services, and set a charge of 5 roubles for Ordinary letters sent abroad and 10 roubles for Registered.
With the final defeat of Red forces in the second half of 1919, Latvia successfully asserted its Independence, though the Moscow government did not formally recognise Latvian independence until August 1920. Nonetheless, in the intervening period Latvia had become a Foreign Destination as far as mail was concerned. This is illustrated by the fact that the cover below sent from MOSCOW 25 6 20 to WAINODE 31 7 20 has a Registration label intended for foreign mail, as well as by the fact that it is franked at the Foreign Registered rate of 10 roubles ( 2 x 5 kop x 100 = 10 roubles) and not the Domestic Registered rate of 7 roubles: