quickies

netstat -r -n
to look at routing table

route add <badip> 127.0.0.1
I use this to block badips sending bad data/exploits to the server (amongst other methods)
you can also send the trafic to /dev/null

route delete <formerbadip> 127.0.0.1
to unblock an ip blocked by the above command

/var/qmail/bin/qmail-qstat
to check the queue for qmail