PHP - Mail script (Select element) - php

Question

I have been working on a website recently from a website template (Puremedia). The template originally had a working contact form. It consisted of "First name", "last name", "Email" and "Subject". And then of course the message. I have now replaced the "Last name" text-box with a dropdown menu. I have done so by using the html select tags. Now my question is how I would change the php scripting so that instead of sending the message (Contact form) to One predefined email. It can send it to two different email adresses. How I would like it to be implemented would be using the dropdown menu. So for example the dropdown menu would be someling along these lines: "Choose Receiver" , "Mail 1" , "Mail 2".
And then also adding a checkbox below the message field that will send a copy to the persons own email address. - Here is my contact form code:
<form name="contactForm" id="contactForm" method="post" action="">
<fieldset>
<div class="row">
<div class="six columns mob-whole">
<label for="contactFname">First Name <span class="required">*</span></label>
<input name="contactFname" type="text" id="contactFname" placeholder="First Name" value="" />
</div>
<div class="six columns mob-whole">
<select name="mailacc">
<option value="1">Send til (Vælg venligst)</option>
<option value="2">Direktør</option>
<option value="3">Bogholder</option>
</select>
</div>
</div>
<div class="row">
<div class="six columns mob-whole">
<label for="contactEmail">Email <span class="required">*</span></label>
<input name="contactEmail" type="text" id="contactEmail" placeholder="Email" value="" />
</div>
<div class="six columns mob-whole">
<label for="contactSubject">Subject</label>
<input name="contactSubject" type="text" id="contactSubject" placeholder="Subject" value="" />
</div>
</div>
<div class="row">
<div class="twelve columns">
<label for="contactMessage">Message <span class="required">*</span></label>
<textarea name="contactMessage" id="contactMessage" placeholder="Your Message" rows="10" cols="50" ></textarea>
</div>
</div>
<div>
<button class="submit full-width">Send Message</button>
<div id="image-loader">
<img src="images/loader.gif" alt="" />
</div>
</div>
</fieldset>
</form> <!-- /contactForm -->
<!-- message box -->
<div id="message-warning"></div>
<div id="message-success">
<i class="fa fa-check"></i>Your message was sent, thank you!<br />
</div>
</div> <!-- /contact-form -->
The PHP part:
<?php
// Replace this with your own email address
$siteOwnersEmail = 'mail#domain.com';
if($_POST) {
$fname = trim(stripslashes($_POST['contactFname']));
$lname = trim(stripslashes($_POST['contactLname']));
$email = trim(stripslashes($_POST['contactEmail']));
$subject = trim(stripslashes($_POST['contactSubject']));
$contact_message = trim(stripslashes($_POST['contactMessage']));
// Check First Name
if (strlen($fname) < 2) {
$error['fname'] = "Please enter your first name.";
}
// Check Last Name
if (strlen($lname) < 2) {
$error['lname'] = "Please enter your last name.";
}
// Check Email
if (!preg_match('/^[a-z0-9&\'\.\-_\+]+#[a-z0-9\-]+\.([a-z0-9\-]+\.)*+[a-z]{2}/is', $email)) {
$error['email'] = "Please enter a valid email address.";
}
// Check Message
if (strlen($contact_message) < 15) {
$error['message'] = "Please enter your message. It should have at least 15 characters.";
}
// Subject
if ($subject == '') { $subject = "Contact Form Submission"; }
// Set Name
$name = $fname . " " . $lname;
// Set Message
$message .= "Email from: " . $name . "<br />";
$message .= "Email address: " . $email . "<br />";
$message .= "Message: <br />";
$message .= $contact_message;
$message .= "<br /> ----- <br /> This email was sent from your site's contact form. <br />";
// Set From: header
$from = $name . " <" . $email . ">";
// Email Headers
$headers = "From: " . $from . "\r\n";
$headers .= "Reply-To: ". $email . "\r\n";
$headers .= "MIME-Version: 1.0\r\n";
$headers .= "Content-Type: text/html; charset=ISO-8859-1\r\n";
if (!$error) {
ini_set("sendmail_from", $siteOwnersEmail); // for windows server
$mail = mail($siteOwnersEmail, $subject, $message, $headers);
if ($mail) { echo "OK"; }
else { echo "Something went wrong. Please try again."; }
} # end if - no validation error
else {
$response = (isset($error['fname'])) ? $error['fname'] . "<br /> \n" : null;
$response .= (isset($error['lname'])) ? $error['lname'] . "<br /> \n" : null;
$response .= (isset($error['email'])) ? $error['email'] . "<br /> \n" : null;
$response .= (isset($error['message'])) ? $error['message'] . "<br />" : null;
echo $response;
} # end if - there was a validation error
}
?>