What makes you think your mailed vote can possibly be secret?
https://reason.com/volokh/2021/01/20/is-the-president-an-officer-of-the-united-states-for-purposes-of-section-3-of-the-fourteenth-amendment/
https://reason.com/volokh/2021/01/20/is-the-president-an-officer-of-the-united-states-for-purposes-of-section-3-of-the-fourteenth-amendment/