How to configure SparkPost in Laravel 1.5?

I use SparkPost mail server to send emails in Laravel.

When I try to send one email I get an error:

"Client error: `POST https:\/\/api.sparkpost.com\/api\/v1\/transmissions` resulted in a `400 Bad Request` response:\n{ \"errors\": [ { \"message\": \"Invalid domain\", \"description\": \"No sending domain specified\", \"code\": \"7001\" } ] }\n"

My configuration is:

services.php

'sparkpost' => [
        'secret' => "key-api",
    ],

mail.php:

'driver' => env('MAIL_DRIVER', 'sparkpost'),

via Chebli Mohamed