# server

named-checkconf

ss -tuna4

sudo -u named rndc status

dig @127.0.0.1 apple.com -t A | grep -v "^;"
dig @127.0.0.1 alpha.lab.example.net -t A | grep -v "^;"

ss -tna4 | grep :25

postfix check

# client

nmap -sU -p53 10.18.0.5

dig @10.18.0.5 amazon.com -t A | grep -v "^;"
dig @10.18.0.5 alpha.lab.example.net -t A | grep -v "^;"
dig kernel.org -t A | grep -v "^;"

nslookup -query=A google.com

nmap -p25 10.18.0.5

tail -f /var/log/maillog &