I have faced the same problem and I have fixed. Please make sure some things as written bellow :
Mail::send('emails.auth.activate', array('link'=> URL::route('account-activate', $code),'username'=>$user->username),function($message) use ($user) {
$message->to($user->email , $user->username)->subject('Active your account !');
});
This should be your emails.activation
Hello {{ $username }} , <br> <br> <br>
We have created your account ! Awesome ! Please activate by clicking the following link <br> <br> <br>
----- <br>
{{ $link }} <br> <br> <br>
----
The answer to your why you can't call $email variable into your mail sending function. You need to call $user variable then you can write your desired variable as $user->variable
Thank You :)