<?php
// Key for API at apilayer.net
define('ACCESS_KEY', 'dcbd625c3505e499416fbaf36ba9a087');
// Here we will store an errors
$errors = array();
// https://pastebin.com/1TGZ4fB5
// Check email with regex
function validEmail($str) {
    return (!preg_match("/^([a-z0-9\+_\-]+)(\.[a-z0-9\+_\-]+)*@([a-z0-9\-]+\.)+[a-z]{2,6}$/ix", $str)) ? FALSE : TRUE;
}

/**
 * @param $email
 * @return bool
 */
function scoringEmail($email){
    $params = array(
        'access_key' => ACCESS_KEY,
        'email' => $email,
        'smtp' => '1',
        'format' => '1',
    );
    $url = "http://apilayer.net/api/check?".http_build_query($params);
    $response = file_get_contents($url);
    if($response === false){
        return false;
    }
    // If we are here - we have response!
    $response = json_decode($response, true);
    //var_dump($response); exit;
    if(isset($response['smtp_check'])){
        return (bool)$response['smtp_check'];
    }

    return false;
}

/**
 * Get subscriber email
 */
if(isset($_POST['email'])){
    // It means that we have at least the field
    // But we don't know if it is real and OK
    $email = strtolower(trim($_POST['email']));
    // Is syntax not correct?
    if (!validEmail($email)){
        $errors[] = 'Your email is not valid!';
    } elseif(!scoringEmail($email)) {
        $errors[] = 'Your email has low score!';
    }
}