Find all the IP addresses that have no reverse DNS.
cat /var/log/exim/mainlog | grep reverse | awk ‘{print $13}’ | grep ‘^[0-9]\{ 1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}$’ | unique
Find all viruses
cat /var/log/exim/mainlog | grep virus | awk ‘{print $17}’ | grep -v virus