Check user authentication with SMTP

test_mail_server_auth.sh

#!/usr/bin/env bash                                                                                                              

[[ $@ ]] || {
    printf "Usage\n\t./$0 server username password\n"
    exit 1
}

SERVER=$1
MAILUSER=$2
PASSWORD=$3

AUTH_STRING=`echo -n -e "$MAILUSER\0$MAILUSER\0$PASSWORD" | openssl base64 -e`

{
    sleep 1
    echo "EHLO $HOSTNAME"
    sleep 1
    echo "AUTH PLAIN $AUTH_STRING"
    sleep 5
    echo "QUIT"
} | telnet $SERVER 587