Emails sent by php end up in the spam folder

I'm sending some emails for php but these end up in the spam folder. Is something missing?

<?php
    $mail = file_get_contents('../index.html');
    $titulo = "asunto";
    $headers = "MIME-Version: 1.0\r\n"; 
    $headers .= "Content-type: text/html; charset=iso-8859-1\r\n"; 
    $headers .= "From: Walls Barbershop <el correo desde el que envio>\r\n";
    $Headers .= "X-Sender: <el correo desde el que envio>\r\n";
    $Headers .= "X-Mailer: PHP\r\n"; 
    $Headers .= "X-Priority: 1\r\n"; 
    $Headers .= "Return-Path: <el correo desde el que envio>\r\n";
    $headers .= "Reply-To: el correo desde el que envio\r\n";
    $to ="el correo destino";

    $bool = mail($to, $titulo, $mail, $headers);
?>