vi /etc/default/exim4 
vi update-exim4.conf.conf
 
update-exim4.conf
 
vi exim4.conf.template
 
systemctl restart exim4.service 
 
netstat -tulpn|grep 25
 
most /var/log/exim4/rejectlog
most /var/log/exim4/paniclog
most /var/log/exim4/mainlog
most /var/log/mail.err
most /var/log/mail.log