In cPanel a users email files are stored in

/home/USER/mail/domain.com/user/

There is a hidden linked shortcut in

/home/USER/mail/.username.domain.com/

Spam Assassin settings are stored in

/home/username/.spamassassin/user_prefs

Email Logs

/var/log/exim_mainlog
/usr/local/cpanel/logs/login_log