I contribute this, for anyone who uses yahoogroups and and will know they have a huge pool of email servers. This can be adapted for other mail lists also. Request for Comment. for i in `seq 0 255` ; do IP=`ping n$i.grp.scd.yahoo.com -c 1 -i 100 | grep icmp_seq=0 | sed s/.*from\ //|sed s/:\ icmp.*//` ; touch $IP ; done ;