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PBEM Helper
In short, PBEM Helper automates the playing, sending e-mails and hosting. From the readme:
If you are running Host, make sure that e-mail address field contains the e-mail addresses of all players, separated by ; character. If there is only one extra player besides you, you still need to add ; into end of e-mail address, so that PBEM Helper knows that you are the host. When all players have sent their .2h file to you, then the game status changes to Host. Double click the game to generate the turn. Host will send the following files to all players: ftherlnd, *.trn. If you have Automatic Play enabled, all this happens automatically.
If you are just a player, make sure that the e-mail address contains the host's e-mail address. Player will send just one .2h file.
If you want to use the password sending with Ctrl+Shift+P, make sure that the password contains only numbers, not letters.