SMTP relay check on multiple subdomains

smt_relay_check.sh

#!/usr/bin/env bash
declare -a arr=("25" "465" "587" "2525")

for i in `cat smtp_hosts`;
do
k=`dig +short $i | tail -n1`
if [ -z "$k" ]
then
      echo "No ip present corresponding to hostname" $i
else
for j in "${arr[@]}";
do
echo "testing mail relay for ${i}:${j}"
my_email_body="Test from telnet from host ${i}:${j}"
mail_server_ip=$k
mail_server_port=$j
recipient="user@gmail.com"
sender="\"VulnDomain Support\"<support@vulndomain.com>"

nc ${mail_server_ip} ${mail_server_port} << EOF
ehlo vulndomain.com
mail from:${sender}
rcpt to:${recipient}
data
From:${sender}
To:${recipient}
subject: Telnet test
${my_email_body}
.
quit
EOF
done
fi
done