If you reply to an email it places a arrow pointing left, next to the person it is from, if I export my emails ( Backup) this arrow disappears, when you check backup. So, it appears you will lose all your replied to info if you restore.
Exporting messages is not a backup.
The replied and forwarded information is stored in the message database in eM Client, and not the message itself. If you backup using Menu > File > Backup, this message history will be preserved when you restore using Menu > File > Restore.
Thanks Gary, that explains why it is missing…