Where does KMail save my settings and my mail?
Most KMail settings are stored in $KDEHOME/share/config/kmailrc, where $KDEHOME is typically ~/.kde; the identities are stored in $KDEHOME/share/config/emailidentities and your mail is saved in $KDEHOME/share/apps/kmail (or ~/Mail if you upgraded from a previous KMail version that used this location.) Note that some of the files are hidden: remember to also copy those if you want to backup or archive your mails.