WP_Mail无法触发，并且无法在实时服务器上发送邮件

Question

美好的一天，我在functions.php文件中写了一些代码，一旦所有发布的帖子都用关键字更新，它将把电子邮件发送给网站所有者。 （与数据库有关）。

   global $wpdb;
     // Calculate whether all posts are updated
     $getToTalUnUpdatedPosts = $wpdb ->get_var(
        "select count(*) from wp_posts where check_key = 0 and post_type = 'post' and post_status='publish'"
    );
    $getToTalUpdatedPosts = $wpdb ->get_var(
        "select count(*) from wp_posts where check_key = 1 and post_type = 'post' and post_status='publish'"
    );
     // send email to inform once there's no posts left unupdated
    if( $getToTalUnUpdatedPosts == 0){
        $email = get_option("email_error_id") != "" ?  get_option("email_error_id") : "myEmail@gmail.com";
        var_dump($email); //get email of the receiver 
        $subject_mail = 'All posts with keywords updated completely';
        $calculate_total_published_posts = $wpdb -> get_var(
            "select count(*) from wp_posts where post_type= 'post' and post_status='publish' and post_content != ''"
        );
        $message_content = '<p> Total posts in your database : '. $calculate_total_published_posts . '</p>
            <p> Total posts updated with keywords : ' .$getToTalUpdatedPosts. '</p> ';
            $headers =  'MIME-Version: 1.0' . "\r\n";
            $headers .= 'Content-type: text/html; charset=utf-8' . "\r\n"; 
            var_dump($headers);
        $success = wp_mail($email, $subject_mail, $message_content , $headers);
        var_dump($success);
    }

但是，$success的调试值始终返回false，我无法收到任何电子邮件。 我的网站也支持SMTP，但是此操作无法触发。