#!/bin/bash

# aufruf backscatter.sh empfängerdomain

egrep "User unknown; from=<>.*$1" /var/log/mail.log |\
	grep -v "from unknown" |\
	cut -d "]" -f2|\
	cut -d "[" -f2|\
	sort -b -t. -k1,1n -k2,2n -k3,3n -k4,4n|\
	uniq -c|\
	less