Where does it go wrong? Just to be sure, have you set the game type to "play by email" (default is "hotseat"). See attached image for an indication of what to do.
View attachment 39536
After "OK", the first thing to happen should be a prompt for a password (This password must be used when opening your opponent's reply). After that, the turn is played as usual. When the turn ends, you are prompted to save the game in PBL format, then TOAW closes down. All you have to do now is sending the PBL file to your opponent by email. Hope this clarifies.
Regards
Martin