Debug why a Queue failed on Laravel 5.2 - php

Question

I'm trying to dispatch Welcome Email on Laravel 5.2 but the job is failing and I have no idea how to figure out why.
Here is what I have so far:
public function test(Request $request) {
$email = $request->get('email');
$subject = $this->word('emails.welcome.subject');
// Mail::send # I use this to Send it synchronously
// $this->mailQueue->queue # I use this to Queue
('emails.welcome', ['domain' => 'blablabla', 'name' => 'Marco Aurélio Deleu', 'date' => Carbon::now(),
'total' => 100, 'pretext' => '', 'score' => '', 'surtext' => '', 'password' => 'blabla', 'shop' => ''],
function ($message) use ($email, $subject) {
$message->to($email);
$message->subject($subject);
}, true);
return 'queued';
}
I noticed that Jobs can easily fail when any kind of exception is thrown, so I figured that I could use Mail::send to find out which exception was being thrown / what was the problem and then use the $this->mailQueue->queue() when I had it sorted out.
I managed to use this strategy to find out that I can't use function calls inside the closure, but now I just don't know what else to do in order to find where the problem lies. The synchronous method of sending the email directly works just fine and the email arrives, but the job will fail at a queue.
The last piece of evidence that I have is that the problem is in the $data array, because if I use it without any $data, the job will be processed and the email arrives.
...
// If I use it like this, it will work perfectly.
$this->mailQueue->queue
('emails.welcome', [ /* empty array */ ], function ($message) use ($email, $subject) {
$message->to($email);
$message->subject($subject);
}, true);
Here is the Queue Listener:
// --> This is the job failing with $data array <--
[06:34 PM]-[root#local]-[/project/]-[git sign-up-with-email]
# php artisan queue:listen --timeout=30 --tries=1
[2016-06-28 21:34:29] Failed: mailer#handleQueuedMessage
^C
// --> This is the job working with empty $data array <--
[06:35 PM]-[root#local]-[/project/]-[git sign-up-with-email]
# php artisan queue:listen --timeout=30 --tries=1
[2016-06-28 21:44:31] Processed: mailer#handleQueuedMessage