Presta-contact-ban/override/controllers/front/ContactController.php

<?php
class ContactController extends ContactControllerCore
{
    public function postProcess()
    {
        session_start();
        $_SESSION["bannedctc"] = "notbanned";
        $_SESSION["ipo"] = "";
        $filename = _PS_ROOT_DIR_ . '/banned.txt';

        if (Tools::isSubmit('submitMessage')) {

            //$message = Tools::getValue('message');
            $from = Tools::getValue('from');
            $ip_address = Tools::getRemoteAddr();

            if (isset($ip_address) && $ip_address != null) {
                if (filter_var($ip_address, FILTER_VALIDATE_IP)) {
                    //$_SESSION["ipo"] = $this->dnsbllookup($ip_address); /*check IP address against DNSBL*/
                    //if($_SESSION["ipo"] == 'listed'){$_SESSION["bannedctc"] = "banned";}
                    $_SESSION["ipo"] = $this->emaillookup($ip_address, $from); /*check email adress and IP address against DNSBL*/
                    $data = json_decode($_SESSION["ipo"], true);
                    if (isset($data['threat'])) {
                        $_SESSION["bannedctc"] = "banned";
                    }
                }
            }

            if (file_exists($filename)) {
                $banned_in_email = array();
                $target = Context::getContext()->link->getPageLink('contact');
                try {
                    $file = preg_replace("/(^[\r\n]*|[\r\n]+)[\s\t]*[\r\n]+/", "\n", $filename);
                    $file = new SplFileObject($file);
                } catch (LogicException $exception) {
                    die('SplFileObject : ' . $exception->getMessage());
                }
                while ($file->valid()) {
                    $line = $file->fgets();
                    array_push($banned_in_email, trim($line));
                }
                $file = null;

                foreach ($banned_in_email as $string) {
                    if (strstr($from, $string)) {
                        $_SESSION["bannedctc"] = "banned";
                    }
                }
            }
        }

        /*  printf($_SESSION["bannedctc"]);
        die(); */
        if ($_SESSION["bannedctc"] == "banned") {
            $this->errors[] = $this->trans('Invalid email address.', [], 'Shop.Notifications.Error');
        }

        parent::postProcess();
    }

    /**
     * The IP-address to be looked up.
     * @param string $ip
     */
    protected function dnsbllookup($ip)
    {
        // Add your preferred list of DNSBL's
        $dnsbl_lookup = [
            "dnsbl-1.uceprotect.net",
            "dnsbl-2.uceprotect.net",
            "dnsbl-3.uceprotect.net",
            "dnsbl.dronebl.org",
            "dnsbl.sorbs.net",
            "zen.spamhaus.org",
            "bl.spamcop.net",
            "list.dsbl.org"
        ];

        $listed = "";

        if ($ip) {
            $reverse_ip = implode(".", array_reverse(explode(".", $ip)));
            foreach ($dnsbl_lookup as $host) {
                if (checkdnsrr($reverse_ip . "." . $host . ".", "A")) {
                    $listed .= $reverse_ip . '.' . $host . ' <span style="color:red">Listed</span>';
                }
            }
        }

        if (empty($listed)) {
            return '"A" record was not found';
        } else {
            return $listed;
        }
    }

    //email check via spammaster.otg - account laurent.desmarets@solido.com
    protected function emaillookup($ip, $address)
    {
        $url = 'https://www.spammaster.org/api/';
        $agent = '8e4c82d4b1c7sdrd058763a52b5b0';
        $data = array(

            'key' => "8e4c82d4b1c7sdrd058763a52b5b0",
            'ip' => $ip,
            'email' => $address,
        );
        $data = http_build_query($data);
        $ch = curl_init($url);
        curl_setopt($ch, CURLOPT_POST, 1);
        curl_setopt($ch, CURLOPT_USERAGENT, $agent);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        $result = curl_exec($ch);
        curl_close($ch);

        // Returns the result of the scan.
        return $result;
    }
}