Php 联系人表单将发送电子邮件，但当我回复时，它会出错

我的联系人表单上的“发送”按钮将电子邮件发送到myaddress@myaddress.com. 但是当我从电子邮件地址回复时，我得到了一个错误，不知道它可能在哪里

错误是：

消息未发送。未采取请求的操作：邮箱不可用 服务器答复： 550您的发件人地址（gmail.com，“我”）必须匹配 您的已验证电子邮件域（domainname.com）

将此视为 伪造的电子邮件。我一时说不出话来。我已经搜索了php文件和联系方式，但我没有gmail地址。php文件代码如下所示：

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

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

            $email_subject = "Message from website";


            function died($error) {
                // your error code can go here
                echo "We are very sorry, but there were error(s) found with the form you submitted. ";
                echo "These errors appear below.<br /><br />";
                echo $error."<br /><br />";
                echo "Please go back and fix these errors.<br /><br />";
                die();
            }

            // validation expected data exists
            if(!isset($_POST['first_name']) ||
                !isset($_POST['last_name']) ||
                !isset($_POST['email']) ||
                !isset($_POST['telephone']) ||
                !isset($_POST['comments'])) {
                died('We are sorry, but there appears to be a problem with the form you submitted.');       
            }

            $first_name = $_POST['first_name']; // required
            $last_name = $_POST['last_name']; // required
            $email_from = $_POST['email']; // required
            $telephone = $_POST['telephone']; // not required
            $comments = $_POST['comments']; // required

            $error_message = "";
            $email_exp = '/^[A-Za-z0-9._%-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}$/';
          if(!preg_match($email_exp,$email_from)) {
            $error_message .= 'The Email Address you entered does not appear to be valid.<br />';
          }
            $string_exp = "/^[A-Za-z .'-]+$/";
          if(!preg_match($string_exp,$first_name)) {
            $error_message .= 'The First Name you entered does not appear to be valid.<br />';
          }
          if(!preg_match($string_exp,$last_name)) {
            $error_message .= 'The Last Name you entered does not appear to be valid.<br />';
          }
          if(strlen($comments) < 2) {
            $error_message .= 'The Comments you entered do not appear to be valid.<br />';
          }
          if(strlen($error_message) > 0) {
            died($error_message);
          }
            $email_message = "Form details below.\n\n";

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

            $email_message .= "First Name: ".clean_string($first_name)."\n";
            $email_message .= "Last Name: ".clean_string($last_name)."\n";
            $email_message .= "Email: ".clean_string($email_from)."\n";
            $email_message .= "Telephone: ".clean_string($telephone)."\n";
            $email_message .= "Comments: ".clean_string($comments)."\n";


        // create email headers
        $headers = 'From: '.$email_from."\r\n".
        'Reply-To: '.$email_from."\r\n" .
        'X-Mailer: PHP/' . phpversion();
        @mail($email_to, $email_subject, $email_message, $headers);  
        ?>

<form name="htmlform" method="post" action="html_form_send.php">
<table width="450px">
</tr>
<tr>
 <td valign="top">
  <label for="first_name">First Name *</label>
 </td>
 <td valign="top">
  <input  type="text" name="first_name" maxlength="50" size="30">
 </td>
</tr>

<tr>
 <td valign="top"">
  <label for="last_name">Last Name *</label>
 </td>
 <td valign="top">
  <input  type="text" name="last_name" maxlength="50" size="30">
 </td>
</tr>
<tr>
 <td valign="top">
  <label for="email">Email Address *</label>
 </td>
 <td valign="top">
  <input  type="text" name="email" maxlength="80" size="30">
 </td>

</tr>
<tr>
 <td valign="top">
  <label for="telephone">Telephone Number</label>
 </td>
 <td valign="top">
  <input  type="text" name="telephone" maxlength="30" size="30">
 </td>
</tr>
<tr>
 <td valign="top">
  <label for="comments">Comments *</label>
 </td>
 <td valign="top">
  <textarea  name="comments" maxlength="1000" cols="25" rows="6"></textarea>
 </td>

</tr>
<tr>
 <td colspan="2" style="text-align:center">
  <input type="submit" value="Submit">
 </td>
</tr>
</table>
</form>

此php文件另存为html_form_send.php。我的表格联系人代码如下：

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

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

            $email_subject = "Message from website";


            function died($error) {
                // your error code can go here
                echo "We are very sorry, but there were error(s) found with the form you submitted. ";
                echo "These errors appear below.<br /><br />";
                echo $error."<br /><br />";
                echo "Please go back and fix these errors.<br /><br />";
                die();
            }

            // validation expected data exists
            if(!isset($_POST['first_name']) ||
                !isset($_POST['last_name']) ||
                !isset($_POST['email']) ||
                !isset($_POST['telephone']) ||
                !isset($_POST['comments'])) {
                died('We are sorry, but there appears to be a problem with the form you submitted.');       
            }

            $first_name = $_POST['first_name']; // required
            $last_name = $_POST['last_name']; // required
            $email_from = $_POST['email']; // required
            $telephone = $_POST['telephone']; // not required
            $comments = $_POST['comments']; // required

            $error_message = "";
            $email_exp = '/^[A-Za-z0-9._%-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}$/';
          if(!preg_match($email_exp,$email_from)) {
            $error_message .= 'The Email Address you entered does not appear to be valid.<br />';
          }
            $string_exp = "/^[A-Za-z .'-]+$/";
          if(!preg_match($string_exp,$first_name)) {
            $error_message .= 'The First Name you entered does not appear to be valid.<br />';
          }
          if(!preg_match($string_exp,$last_name)) {
            $error_message .= 'The Last Name you entered does not appear to be valid.<br />';
          }
          if(strlen($comments) < 2) {
            $error_message .= 'The Comments you entered do not appear to be valid.<br />';
          }
          if(strlen($error_message) > 0) {
            died($error_message);
          }
            $email_message = "Form details below.\n\n";

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

            $email_message .= "First Name: ".clean_string($first_name)."\n";
            $email_message .= "Last Name: ".clean_string($last_name)."\n";
            $email_message .= "Email: ".clean_string($email_from)."\n";
            $email_message .= "Telephone: ".clean_string($telephone)."\n";
            $email_message .= "Comments: ".clean_string($comments)."\n";


        // create email headers
        $headers = 'From: '.$email_from."\r\n".
        'Reply-To: '.$email_from."\r\n" .
        'X-Mailer: PHP/' . phpversion();
        @mail($email_to, $email_subject, $email_message, $headers);  
        ?>

<form name="htmlform" method="post" action="html_form_send.php">
<table width="450px">
</tr>
<tr>
 <td valign="top">
  <label for="first_name">First Name *</label>
 </td>
 <td valign="top">
  <input  type="text" name="first_name" maxlength="50" size="30">
 </td>
</tr>

<tr>
 <td valign="top"">
  <label for="last_name">Last Name *</label>
 </td>
 <td valign="top">
  <input  type="text" name="last_name" maxlength="50" size="30">
 </td>
</tr>
<tr>
 <td valign="top">
  <label for="email">Email Address *</label>
 </td>
 <td valign="top">
  <input  type="text" name="email" maxlength="80" size="30">
 </td>

</tr>
<tr>
 <td valign="top">
  <label for="telephone">Telephone Number</label>
 </td>
 <td valign="top">
  <input  type="text" name="telephone" maxlength="30" size="30">
 </td>
</tr>
<tr>
 <td valign="top">
  <label for="comments">Comments *</label>
 </td>
 <td valign="top">
  <textarea  name="comments" maxlength="1000" cols="25" rows="6"></textarea>
 </td>

</tr>
<tr>
 <td colspan="2" style="text-align:center">
  <input type="submit" value="Submit">
 </td>
</tr>
</table>
</form>

名字*
是什么让你认为这与你的代码有关。如果电子邮件发送正确，那么问题肯定在于您用来回复电子邮件地址的电子邮件客户端

你用什么回复电子邮件地址？
我想是服务器端。我发现邮件客户端有一个重定向，所以我把它取了下来，现在一切都很好。谢谢