Wrong 'from' mail

[A_AZAZEL_A]

hi there!
I use this code to send mail:
$host = "ssl://smtp.gmail.com";
$port = "465";
$username = "...";
$password = "...";

$headers = array ('From' => $from,
'To' => $to,
'Subject' => $subject,'Content-type' => 'text/html');
$smtp = Mail::factory('smtp',
array ('host' => $host,
'port' => $port,
'auth' => true,
'username' => $username,
'password' => $password));

$mail = $smtp->send($to, $headers, $body);

...and the from section of the mail that is received will be the gmail one.
Can you tell me why is that and how can it be the one that is in var $from?