L4: Mail::queue error Address in mailbox given [] does not comply with RFC 2822, 3.6.2

L4: Mail::queue error Address in mailbox given [] does not comply with RFC
2822, 3.6.2

I got an error when I replace send to queue in sending emails. Here's my
code:
foreach ($recs as $rec)
{
$em = $rec->email;
Mail::queue('emails.newsletter',$data,
function($message) use(&$em) {
$message->to($em)->subject('Newsletter | Bla Bla');
});
}
My mail Driver is smtp and the host is relay-hosting.secureserver.net from
godaddy.
It works fine if I'll use Mail::send rather than Mail::queue