To follow the steps below you'll need root access to your server, so you have access to the Exim mail log.
For cPanel Server :
grep cwd /var/log/exim_mainlog | grep -v /var/spool | awk -F"cwd=" '{print $2}' | awk '{print $1}' | sort | uniq -c | sort -n
For Other Server :
For Other Server :
grep cwd /var/log/exim/main.log | grep -v /var/spool | awk -F"cwd=" '{print $2}' | awk '{print $1}' | sort | uniq -c | sort -n
