interface MailHandlerInterface

interface MailHandlerInterface {
    
    /**
     * Sends mail messages as appropriate for a given Message form submission.
     *
     * Can potentially send up to three messages as follows:
     * - To the configured recipient;
     * - Auto-reply to the sender; and
     * - Carbon copy to the sender.
     *
     * @param \Drupal\contact\MessageInterface $message
     *   Submitted message entity.
     * @param \Drupal\Core\Session\AccountInterface $sender
     *   User that submitted the message entity form.
     *
     * @throws \Drupal\contact\MailHandlerException
     *   When unable to determine message recipient.
     */
    public function sendMailMessages(MessageInterface $message, AccountInterface $sender);

}