Page 11 of the manual explains it:
[h=3]Play by Email (PBEM)[/h]EAW can be played against one or two humans opponents using PBEM or any other valid file transfer protocol, such as Instant Messaging or Dropbox™ . One of the players (the “Host”

will have to initiate the game. The procedure is detailed below:
- Create a game:
The Hosting player chooses a Campaign/Scenario and a side and starts the game as usual. This automatically generates a sub-folder in the <User Directory>\EAW\Saves\ directory, named after the Campaign or Scenario selected (1914 Campaign if you play the “1914 Campaign” scenario, for example). Please note that a number helps differentiate between multiple instances of the same Campaign/Scenario. However, the best way to avoid confusion is to rename the in-game files with the appropriate button in the Load Game Window (e.g. 1914 Campaign John vs. Joe). Do NOT rename any EAW files externally to the game.
If you have trouble finding your User Directory, you can look at the Options window, in the main menu, it will be indicated there.
In this newly created folder you will a single HST file, containing all game data.
- Host sends the HST file to opponent:
The Hosting player now sends his opponent the
HST file. The opponent must store this file in a folder of his choice within <User Directory>\EAW\Saves\. It is advisable to use a specific subfolder per game, for example <User Directory>\EAW\Saves\JohnVsJoe subfolder.
Note: In order to avoid possible data corruption if transferred by E-mail, it is strongly advised to E-Mail using some type of compressed format such as ZIP or RAR.
- Non-Host sends ORD file to Host:
Each player now loads the game and gives his orders for the upcoming turn. When ready, each player saves the game. This will generate an
ORD file (in the folders mentioned above).
Important: do
not click on
End Turn at this step.
The Non-Hosting player then sends his
ORD file to the Hosting player.
- Host resolves turn
The Hosting player saves the
ORD file received from his opponent into the appropriate directory (there should be one HST file and then one ORD file per active player) and loads the game again (or if he is not playing, he loads a turn from any player). He now clicks on
End Turn to launch the turn resolution, where all orders are then executed. A new turn is now ready to start. Go back to step # 2 and repeat.
Note: The Non-Hosting player doesn’t get by default a “play back” of his opponent’s turn. However, he can check the turn’s Message Log to see what has occurred during the turn, including battle reports. There is an unofficial playback support though, that can be activated in-game. Please refer to the EAW forum at Ageod on this topic.