U

From:
John Leach's Encyclopedia of Postal Authorities :

UAE - Uzbekistan

UAE - Uzbekistan

UAE
UAR
Ubangi-Shari
Ubangi-Shari-Chad
Uganda
Uganda Protectorate
UK
Ukraine
Ukraine (pre-Soviet)
Ukraine (German Occupation)
Ukrainian Field Post
UKTT
Ultramar
Umm Al Qiwain
UN
UN Administration of West New Guinea
UNESCO
Union Island
Union Islands
Union of Soviet Socialist Republics (USSR)
United Arab Emirates (UAE)
United Arab Republic (UAR)
United Kingdom (UK)
United Kingdom Trust Territory (UKTT)
United Nations (UN)
United States of America (USA)
United States of New Granada
Universal Postal Union (UPU)
Upper Senegal & Niger
Upper Silesia
Upper Volta
Upper Volta (French Colony)
Upper Yafa
UPU
Uruguay
USA
US Post Abroad
US Postal Agency in Shanghai
US Post Offices in Japan
USSR
USSR Issues for the Far East
US Virgin Islands
Uzbekistan