Error reading file

[Basadovsky]

Hello!

I launched a PBEM of France '14 with a friend who decided to go for FWWC and PZC, however as soon as I send my save file he can't read it and gets the following error message "Error reading file". However when he creates the game and sends it to me no problem, until I send it back to him. We have the same version of the game, we don't use a mod. I assumed that the problem could come from the firewall but I'd like to hear from people who are more used to the game. 

Have a nice day!