title: Cannot send message without a sender address in laravel 5.4
body: <p>In my <strong>Laravel 5.4</strong> app I want to send an email notification to the user when they <em>signup</em> I have set everything but not work and shown an exception like: </p>
  
  <pre><code>Cannot send message without a sender address
  </code></pre>
  
  <p>I am using <strong>mailtrap</strong>. </p>
  
  <p>I have also run the artisan command <code>php artisan config:cache</code> and <code>php artisan cache:clear</code></p>
  
  <p><strong>This is my .env file</strong>:</p>
  
  <pre><code>MAIL_DRIVER=smtp
  MAIL_HOST=smtp.mailtrap.io
  MAIL_PORT=2525
  MAIL_USERNAME=3e917ca6b3dabc
  MAIL_PASSWORD=05abe282eca67f
  MAIL_ENCRYPTION=tls
  </code></pre>