Mail function using PHP

Question

I am trying to send email through a form but is giving the following error:

Warning: mail(): Failed to connect to mailserver at "localhost" port 25, verify your "SMTP" and "smtp_port" setting in php.ini or use ini_set() in C:\xampp\htdocs\mail_\proc_mail.php on line 18

by localhost and hosted in the service I hired says the message was delivered but did not arrive in my email, follows the codes: HTML:

<form action="contato_valid.php" method="post" class="frm">


<div class="form-group">
    <label for="nome">Nome</label>
    <input type="text" class="form-control" id="nome" name="nome" placeholder="Digite seu nome com sobrenome" required>
  </div>
  <div class="form-group">
    <label for="email">E-mail</label>
    <input type="email" class="form-control" id="email" name="email" placeholder="Digite seu e-mail">
  </div>
  <div class="form-group">
    <label for="telefone">Telefone</label>
    <input type="phone" class="form-control" id="tel" name="tel" placeholder="Digite seu telefone com DDD">
  </div>
  <div class="form-group">
    <label for="assunto">Assunto</label>
    <input type="text" class="form-control" id="assunto" name="assunto" placeholder="Digite o assunto">
  </div>
  <div class="form-group">
    <label for="msg" required>Mensagem</label>
    <textarea class="form-control" id="msg" name="msg" rows="3" placeholder="Digite sua mensagem aqui"></textarea>
  </div>
  <input type="submit" class="btn btn-primary mb-2" value="Confirmar">

PHP:

<?php

$nome = $_POST['nome'];
$email = $_POST['email'];
$tel = $_POST ['tel'];
$assunto = $_POST['assunto'];
$msg = $_POST['msg'];

$headers =  'MIME-Version: 1.0' . "\r\n"; 
$headers .= 'From: ' . "\r\n";
$headers .= 'Content-type: text/html; charset=iso-8859-1' . "\r\n"; 

$enviar = mail("[email protected]", "SMTP Casa de Emaus", 
    "Nome: " . $nome . 
    "<br> E-mail: " . $email . 
    "<br> Telefone:" . $tel . 
    "<br> Assunto: " . $assunto . 
    "<br> Mensagem: " . $msg . $headers);

//$enviar = mail($to, $email, $msg);

if (!$enviar) {
    echo "<script>
    alert('Falha ao enviar mensagem'); location= './index.php';
    </script>";
} else {
    echo "<script>
    alert('Mensagem enviada com sucesso!'); location= './index.php';
    </script>";
}

?>

I have tried everything I remember and that my co-workers helped me, but without success