Add support for alternate domains

src/Mail/Mailer.php

@@ -64,7 +64,7 @@ public function send($view, array $data, Closure $callback, $message = null)
         $message = $this->message->getMessage();
         $files = $this->message->getFiles();
 
-        $domain = $this->config->get('mailgun.domain');
+        $domain = $this->message->getDomain();
         $response = new Response($this->mailgun->post("{$domain}/messages", $message, $files));
 
         return $response;

src/Mail/Message.php

@@ -18,6 +18,11 @@ class Message
      */
     protected $variables = [];
 
+    /**
+     * @var string|null
+     */
+    protected $domain = null;
+
     /**
      * Message constructor.
      *
@@ -281,6 +286,30 @@ public function testmode($enabled = true)
         return $this;
     }
 
+    /**
+     * Override the default Mailgun domain with another domain name registered with Mailgun.
+     *
+     * @param string $domain
+     *
+     * @return void
+     */
+    public function domain($domain)
+    {
+        $this->domain = $domain;
+
+        return $this;
+    }
+
+    /**
+     * Returns the domain name to use to send the message
+     *
+     * @return string
+     */
+    public function getDomain()
+    {
+        return $this->domain !== null ? $this->domain : $this->config->get('mailgun.domain');
+    }
+
     /**
      * Append a custom MIME header to a message.
      *