title: SendGrid not send messages with only Bcc addresses
body: <p>I recently upgraded the SendGrid C# library to the latest version, and I'm unable to send messages with only Bcc addresses.</p>
  
  <p>If I try to add the addresses to the "To" MailAddress[] object, it works and the messages are delivered. If I add the same addresses to the "Bcc" MailAddress[] object, and I don't add anything to the "To" MailAddress[] object, the messages are not processed and delivered.</p>
  
  <p>In both case the DeliverAsync method not return any errors.</p>