I took a backup of the file home/XXXX/.kde/share/aps/kmail generated under 10.2 and performed a complete new installation of 11.0. In order not to loose the old messages I copied the complete aforementioned folder to 11.0 prior to installing KMail. As a result smtp sending mails does not work "no connection to computer smtp.web.de"

I included an other user and configured kmail, wrote a message and smtp worked.
Question: How can I delete the configuration of KMail for a specific user? Which files should I copy after the configuration in order to have access to my old messages?