smtp-verify.sh

#!/bin/bash

#
# smtp email address verification
# using dig and netcat
#
# authored by robert.jaeckel@itz.uni-halle.de
#

checkaddr=$1
fromaddr=$2

netcat=$(which netcat)
fromhost=$(hostname)
dig=$(which dig)

domainname=$(sed -r 's/^(.+)@(.+)$/\2/' <<<$checkaddr)

mxrecord=`$dig +noall +answer mx $domainname|awk -e '{print $6}'|sed -r 's/(.+)\.$/\1/'|head -n1`
if [ -z $mxrecord ]; then mxrecord=$domainname; fi

rm -rf cmd resp
mkfifo cmd resp

echo "$netcat $mxrecord smtp" >&2
$netcat $mxrecord smtp <cmd >resp &

exec 3>cmd

while read cmd; do
	#echo "awaiting response..." >&2
	read -t 10 <resp || { echo "timeout.">&2 ; exit 2; }  #quit on read error e.g. by timeout
	echo "< $REPLY" >&2
	echo "> $cmd" >&2
	echo $cmd >cmd
	#echo "sent cmd" >&2
done <<EOF
HELO $fromhost
MAIL FROM: <$fromaddr>
RCPT TO: <$checkaddr>
QUIT
EOF

exec 3>&-
rm cmd resp

echo $REPLY
code=$(echo $REPLY | awk -e '{ print $1 }')
if [ "$code" = "250" ]; then exit 0; else exit 1; fi