When you receive a document from an unknown email, you can block this email right away as follows:
In your Unfiled (Documents>Unfiled).
- Click the name of the document with the red message "Unrecognized email address" to activate the preview of the document.
- Click the "Block" button.
- The system will show you an alert letting you know that no more emails will be received from that address. Click "OK".
- A confirmation message will show. Click "OK".