From:
John Leach's Encyclopedia of Postal Authorities :

J

Jaffa - Junagadh

Jaffa - Junagadh

Jaffa (Russian Post Office)
Jaipur
Jamaica
Jammu & Kashmir
Janina
Jannina (Italian Post Office)
Japan
Japan (British Commonwealth Occupation)
Japan (American Post Offices)
Japan (British Post Offices)
Japan (French Post Offices)
Japanese Naval Control Area
Japanese Occupation Issues
Japanese Post Offices Abroad
Japanese Taiwan (Formosa)
Jasdan
Java (Japanese Occupation)
Jeend
Jeind
Jersey
Jerusalem (Italian Post Office)
Jerusalem (Russian Post Office)
Jhalawar
Jhind
Jind
Johor
Johore
Jordan
Jubaland
Jugoslavia
Junagadh