我写了这个php邮件发件人代码：

<?php

if($_SERVER["REQUEST_METHOD"] === "POST") {}

if (isset($_POST['submit'])) {
$name = $_POST['name'];
$subject = $_POST['subject'];
$mailFrom = $_POST['mail'];
$phone = $_POST['phone'];
$company = $_POST['company'];
$website = $_POST['website'];
$message = $_POST['message'];

$recaptcha_secret = "xy";
$response = file_get_contents("https://www.google.com/recaptcha/api/siteverify?secret=".$recaptcha_secret."&response=".$_POST['g-recaptcha-response']);
$response = json_decode($response, true);

if($response["success"] === true){
    $mailTo = "[email protected]";
    $headers = "From: ".$mailFrom;
    $txt = "Feladó: ".$name."\nTelefonszám: ".$phone."\nCég: ".$company."\nWeboldal: ".$website."\n\nÜzenet: ".$message;

mail($mailTo, $subject, $txt, $headers);
header("Location: feedback/koszonjuk");
    
    
}else{
    header("Location: feedback/error");
}

}

?>`

它发送电子邮件到我的服务器端的电子邮件地址后，有人填写我的表格在我的网站与recaptcha。
我想有UTF-8字符编码的电子邮件，但我看不到这个问题。这些字符在表单的电子邮件中管理不当：öüóőúéá
表单所在的HTML页面设置为UTF-8。HTML表单代码：

<form action="ajanlatkeres.php" method="post" class="ajanlatkeres-form" accept-charset="utf-8">
                    <h2>Általános adatok</h2>
                        <input type="text" name="name" placeholder="Teljes név*" class="feedback-input" required>
                        <input type="text" name="mail" placeholder="E-mail*" class="feedback-input" required>
                        <input type="text" name="phone" placeholder="Telefonszám*" class="feedback-input" required>
                    <h2>Vállalkozás adatai</h2>
                        <input type="text" name="company" placeholder="Márkanév" class="feedback-input">
                        <input type="text" name="website" placeholder="Weboldal" class="feedback-input">
                    
                    <h2>Üzenet</h2>
                        <input type="hidden" name="subject" value="Ajánlatkérés">
                        <textarea name="message" placeholder="Írj pár sort projektedről*" class="feedback-input" required></textarea>
                        <div class="g-recaptcha" id="rcaptcha" data-theme="dark" data-sitekey="xy"></div>
                        <br/>
                        <button id="submit_form" class="contactbutton" type="submit" name="submit">Küldés</button>
                    </form>

什么原因会导致此问题？这是我的PHP代码吗？