Thanks for make it clearer. =)
Ok, then you will be having 2 files.
---> select.php
<form action="displayemail.php" method="post" name="selectemail">
<select name="department">
<option value="marketing">Marketing Department</option>
<option value="finance">Finance Department</option>
</select>
</form>
---> displayemail.php
<?php
$department=$_POST['department'];
switch ($department){
case "marketing":
$email="marketing@domain.com";
case "finance":
$email="finance@domain.com";
default:
$email="webmaster@domain.com";
}
?>
Click <a href="mailto:<?php print $email; ?>">here</a> to email us!
HTH