我从PHP表单接收没有重音的奇怪文本

I'm making a form with the POST method on a .PHP file but when I receive the e-mail it has lot of strange characters that should be letters with accents.

It looks like this:

<?php
if(isset($_POST['mail'])) {

    // CHANGE THE TWO LINES BELOW
    $email_to = "alala@alala.com";

    $email_subject = "lalala";


    // validation expected data exists
    if(!isset($_POST['nome']) ||
        !isset($_POST['mail']) ||
        !isset($_POST['site']) ||
        !isset($_POST['autorizacao']) ||
        !isset($_POST['banca']) ||
        !isset($_POST['descricao']) ||
        !isset($_POST['mesa'])) {
        died('');       
    }

    $nome = $_POST['nome']; // required
    $mail = $_POST['mail']; // required
    $telefone = $_POST['telefone']; // required
    $site = $_POST['site']; // required
    $autorizacao = $_POST['autorizacao']; // required
    $banca = $_POST['banca']; // required
    $descricao = $_POST['descricao']; // required
    $mesa = $_POST['mesa']; // required
    $sugestoes = $_POST['sugestoes']; // required

    $email_message = "Inscrição para a Showroom:.

";

    function clean_string($string) {
      $bad = array("content-type","bcc:","to:","cc:","href");
      return str_replace($bad,"",$string);
    }

    $email_message .= "Nome: ".clean_string($nome)."
";
    $email_message .= "E-mail: ".clean_string($mail)."
";
    $email_message .= "Email: ".clean_string($telefone)."
";
    $email_message .= "Email: ".clean_string($site)."
";
    $email_message .= "Email: ".clean_string($autorizacao)."
";
    $email_message .= "Email: ".clean_string($banca)."
";
    $email_message .= "Email: ".clean_string($descricao)."
";
    $email_message .= "Email: ".clean_string($mesa)."
";
    $email_message .= "Comments: ".clean_string($sugestoes)."
";


// create email headers
$headers = 'From: '.$email_from."
".
'Reply-To: '.$email_from."
" .
'X-Mailer: PHP/' . phpversion();

    @mail($email_to, $email_subject, $email_message, $headers);
?>

Add encoding to $headers:

// create email headers
$headers = 'From: '.$email_from."
".
'Reply-To: '.$email_from."
" .
"Content-Type: text/plain;charset=utf-8"."
" .
'X-Mailer: PHP/' . phpversion();