免费Bootstrap模板HTML联系表单无法发邮件并报错求助

我正在学习基础网站开发，目前遇到联系表单无法正常工作的问题。使用的是ThemeWagon的免费Bootstrap 4 HTML5建筑公司网站模板，已上传至购买的虚拟主机。

该联系表单依赖4个文件：HTML表单文件、用于设置收件邮箱的contact.php文件、contact.js文件以及负责数据验证的jqBootstrapValidation.min.js文件。以下是各文件代码：

HTML表单代码 #

<div class="col-md-6">
    <div class="contact-form">
        <div id="success"></div>
        <form name="sentMessage" id="contactForm" novalidate="novalidate">
            <div class="control-group">
                <input type="text" class="form-control" id="name" placeholder="Your Name" required="required" data-validation-required-message="Please enter your name" />
                <p class="help-block text"></p>
            </div>
            <div class="control-group">
                <input type="email" class="form-control" id="email" placeholder="Your Email" required="required" data-validation-required-message="Please enter your email" />
                <p class="help-block text"></p>
            </div>
            <div class="control-group">
                <input type="text" class="form-control" id="subject" placeholder="How can we help?" required="required" data-validation-required-message="Please enter a subject" />
                <p class="help-block text-"></p>
            </div>
            <div class="control-group">
                <textarea class="form-control" id="message" placeholder="Message" required="required" data-validation-required-message="Please enter your message"></textarea>
                <p class="help-block text"></p>
            </div>
            <div>
                <button class="btn" type="submit" id="sendMessageButton">Send Message</button>
            </div>
        </form>
    </div>
</div>

contact.php代码 #

<?php
    if(empty($_POST['name']) || empty($_POST['subject']) || empty($_POST['message']) || !filter_var($_POST['email'], FILTER_VALIDATE_EMAIL)) {
      http_response_code(500);
      exit();
    }

    $name = strip_tags(htmlspecialchars($_POST['name']));
    $email = strip_tags(htmlspecialchars($_POST['email']));
    $m_subject = strip_tags(htmlspecialchars($_POST['subject']));
    $message = strip_tags(htmlspecialchars($_POST['message']));

    $to = "myemail@mail.com"; // Change this email to yours //
    $subject = "$m_subject:  $name";
    $body = "You have received a new message from your website contact form.

"."Here are the details:

Name: $name


Email: $email

Subject: $m_subject

Message: $message";
    $header = "From: $email";
    $header .= "Reply-To: $email";  

    if(!mail($to, $subject, $body, $header))
      http_response_code(500);
?>

contact.js代码 #

$(function () {

    $("#contactForm input, #contactForm textarea").jqBootstrapValidation({
        preventSubmit: true,
        submitError: function ($form, event, errors) {
        },
        submitSuccess: function ($form, event) {
            event.preventDefault();
            var name = $("input#name").val();
            var email = $("input#email").val();
            var subject = $("input#subject").val();
            var message = $("textarea#message").val();

            $this = $("#sendMessageButton");
            $this.prop("disabled", true);

            $.ajax({
                url: "contact.php",
                type: "POST",
                data: {
                    name: name,
                    email: email,
                    subject: subject,
                    message: message
                },
                cache: false,
                success: function () {
                    $('#success').html("<div class='alert alert-success'>");
                    $('#success > .alert-success').html("<button type='button' class='close' data-dismiss='alert' aria-hidden='true'>&times;")
                            .append("</button>");
                    $('#success > .alert-success')
                            .append("<strong>Your message has been sent. </strong>");
                    $('#success > .alert-success')
                            .append('</div>');
                    $('#contactForm').trigger("reset");
                },
                error: function () {
                    $('#success').html("<div class='alert alert-danger'>");
                    $('#success > .alert-danger').html("<button type='button' class='close' data-dismiss='alert' aria-hidden='true'>&times;")
                            .append("</button>");
                    $('#success > .alert-danger').append($("<strong>").text("Sorry " + name + ", it seems that our mail server is not responding. Please try again later!"));
                    $('#success > .alert-danger').append('</div>');
                    $('#contactForm').trigger("reset");
                },
                complete: function () {
                    setTimeout(function () {
                        $this.prop("disabled", false);
                    }, 1000);
                }
            });
        },
        filter: function () {
            return $(this).is(":visible");
        },
    });

    $("a[data-toggle=\"tab\"]").click(function (e) {
        e.preventDefault();
        $(this).tab("show");
    });
});

$('#name').focus(function () {
    $('#success').html('');
});

我已将contact.php文件中的收件邮箱修改为个人邮箱以及主机上创建的自定义邮箱，但线上提交表单时，始终收到错误提示：Sorry [姓名], it seems that our mail server is not responding. Please try again later!。试过检查PHP文件首尾标签，将$to改为$email_to，问题仍未解决，求排查线索。

排查方向建议 #

• 检查虚拟主机邮件服务状态：多数虚拟主机默认禁用PHP mail() 函数，或要求用绑定域名的邮箱作为发件人。登录主机控制面板，确认邮件功能是否开启，是否需配置SMTP参数。
• 修复PHP邮件头格式：当前$header拼接缺少换行符，HTTP头必须用\r\n分隔，修正后代码：

  $header = "From: $email\r\n";
  $header .= "Reply-To: $email\r\n";
  

  格式错误会导致邮件被服务器拒收。
• 添加错误日志定位问题：在contact.php的mail()判断后增加日志记录，便于查看具体失败原因：

  if(!mail($to, $subject, $body, $header)){
      error_log("邮件发送失败：" . error_get_last()['message']);
      http_response_code(500);
  }
  

  然后查看主机的PHP错误日志，获取详细报错信息。
• 验证文件路径与权限：确认contact.php的路径和contact.js中url: "contact.php"完全一致，文件权限设置为644，避免因权限不足无法执行。
• 测试基础邮件发送功能：编写最简测试脚本，单独运行确认主机可正常发信：

  <?php
  $to = "你的收件邮箱";
  $subject = "测试邮件";
  $body = "测试内容";
  $headers = "From: 你的域名邮箱@xxx.com\r\n";
  if(mail($to, $subject, $body, $headers)){
      echo "发送成功";
  } else {
      echo "发送失败";
      print_r(error_get_last());
  }
  ?>
  

内容的提问来源于stack exchange，提问作者Toshgarcia