For emails from actual people, our algorithms decide if the person should be sorted into your Inbox or @SaneLater. Our training effects all emails from that person.
Services are different, and often the aspect of the service that is trained is contextually related to the subject of the email. So you might train the receipts of a particular Internet store to @SaneBulk, but the shipping notifications could still go to your @SaneLater folder.
To ensure your privacy, we do not download the body of emails. Therefore, we are limited to decide importance based on the subjects and sender alone.