I can't reply to the sender of the email without cut and paste their address

Question

I have a site currently hosted by yahoo.My PHP form can send emails both to myself and a copy to the sender.

if( isset($_POST) ){

    //form validation vars
    $formok = true;
    $errors = array();

    //$tz=timezone_open("Australia/Brisbane");
    //sumbission data
    $ipaddress = $_SERVER['REMOTE_ADDR'];
    $date = gmdate('D d F Y', time()+(36000));
    //$date = gmdate(' D d F Y');
    //gmdate('D d F Y', time()+(36000));
    $time = gmdate(' H:i:s', time()+36000);


    //form data
    $name = $_POST['name']; 
    $email = $_POST['email'];
    $telephone = $_POST['telephone'];

    $enquiry = $_POST['enquiry'];
    $message = $_POST['message'];

    //validate form data

    //validate name is not empty
    if(empty($name)){
    $formok = false;
    $errors[] = "You have not entered a name";
}

//validate email address is not empty
if(empty($email)){
    $formok = false;
    $errors[] = "You have not entered an email address";
//validate email address is valid
}elseif(!filter_var($email, FILTER_VALIDATE_EMAIL)){
    $formok = false;
    $errors[] = "You have not entered a valid email address";
}

//validate telephone is not empty
if(empty($telephone)){
    $formok = false;
    $errors[] = "You have not entered your cellphone number";
}

//validate message is not empty
if(empty($message)){
    $formok = false;
    $errors[] = "You have not entered a message";
}

//validate message is greater than 20 charcters
elseif(strlen($message) <20){
    $formok = false;
    $errors[] = "Your message must be greater than 20 characters";
}

//send email if all is ok
if($formok){

//      ini_set("sendmail_from","info@example.com");
    ini_set("sendmail_from", '$email'); 


    $headers = 'Content-type: text/html; charset=iso-8859-1' . "\r\n\n" .



    $emailbody = "<pYou has received a new message from the enquiries form.</p
                  <pThis message was sent by {$name} from the IP Address: {$ipaddress} on {$date} at {$time}</p

                  <p<strongName: </strong {$name} </p
                  <p<strongEmail Address: </strong {$email} </p
                  <p<strongTelephone: </strong {$telephone} </p
                  <p<strongEnquiry: </strong {$enquiry} </p
                  <p<strongMessage: </strong {$message} </p";

    mail("info@mywebsite.com", "New Enquiry from website contact form", $emailbody, $headers);

    mail("$email", "{$name} Your Enquiry", $emailbody, $headers);

}


    //what we need to return back to our form
    $returndata = array(
    'posted_form_data' = array(

        'name' = $name,
        'email' = $email,
        'telephone' = $telephone,
        'enquiry' = $enquiry,
        'message' = $message
    ),
    'form_ok' = $formok,
    'errors' = $errors
);


//if this is not an ajax request
if(empty($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) !== 'xmlhttprequest'){
    //set session variables
    session_start();
    $_SESSION['cf_returndata'] = $returndata;

    //redirect back to form
    header('location: http://www.mywebsite.com/thankyou.html');
    //header('location: ' . $_SERVER['HTTP_REFERER']);
}
}

All help will be appreciated