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- Aden
- Aden - Qu'aiti State of Shihr and Mukulla
- Afars and Issas
- Afghanistan [AFG]
- Aitutaki
- Ajman
- Ajman - Manama
- Alawite State
- Albania - Korçë
- Albania [ALB]
- Alderney
- Alexandretta
- Alexandria
- Algeria
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- Allied Occupation - Germany
- Allied Occupation - Germany (American and british zone)
- Allied Occupation - Germany (French zone)
- Allied Occupation - Germany (Soviet zone)
- Allied Occupation - Italy
- Andorra - French
- Andorra - Spanish
- Angola [AGO]
- Angra
- Anguilla
- Anjouan
- Annam & Tonkin
- Antigua
- Antigua and Barbuda - Redonda
- Antigua and Barbuda [ATG]
- Argentina [ARG]
- Armenia
- Aruba
- Ascension Island
- Australia [AUS]
- Australian Antarctic Territory
- Austria - Local post
- Austria [AUT]
- Austria-Hungary - Bosnia and Herzegovina
- Austria-Hungary - Military mail
- Austria-Hungary - Military mail Italy
- Austria-Hungary - Military mail Montenegro
- Austria-Hungary - Military mail Romania
- Austria-Hungary - Military mail Serbia
- Azerbaijan
- Azores