成功重定向后，无法从联系表单获取邮件

Question

我通过联系表单向我的身份证件发送邮件，但没有在我的身份证中收到任何邮件。是的我已经上传到服务器但仍然无法正常工作，这里是代码

contact.html

<form  action="contact.php" method="post">
            <label class="label">Name <em>*</em></label>
            <label class="input">
                <input type="text" name="name" id="name">
            </label>

            <div class="clearfix"></div>

            <label class="label">E-mail <em>*</em></label>
            <label class="input">
                <input type="email" name="email" id="email">
            </label>

            <!-- <div class="clearfix"></div>


            <label class="label">Phone <em>*</em></label>
            <label class="input">
                <input type="text" name="phone" id="phone">
            </label> -->

            <div class="clearfix"></div>

            <label class="label">Subject <em>*</em></label>
            <label class="input">
                <input type="text" name="subject" id="subject">
            </label>

            <div class="clearfix"></div>

            <label class="label">Message <em>*</em></label>
            <label class="textarea">
                <textarea rows="5" name="content" id="message"></textarea>
            </label>

            <div class="clearfix"></div>

            <button type="submit"  name="submit" class="button">Send Message</button>

        </form>

以下是contact.php的代码

<?php 
if(isset($_POST['submit'])){
    $to = "snigdhasrk143@gmail.com"; // this is your Email address
    $from = $_POST['email']; // this is the sender's Email address
    $full_name = $_POST['name'];
    $subject = $_POST['subject'];
    $content = $_POST['content'];
    $subject2 = "Copy of your form submission";
    $message = $full_name . " " . $from . " -- wrote the following:" . "\n\n" . $_POST['content'];
    $message2 = "Here is a copy of your message " . $full_name . "\n\n" . $_POST['content'];

    $headers = "From:" . $from;
    $headers2 = "From:" . $to;
    mail($to,$subject,$message,$headers);
    mail($from,$subject2,$message2,$headers2); // sends a copy of the message to the sender
    header('Location: index.html');
        // You can also use header('Location: thank_you.php'); to redirect to another page.
    }
?>

成功重定向到索引页但没有收到任何邮件？请帮忙