How would you prove that you voted how you said you did?
If you took a picture of your ballot, or even if you filmed yourself putting it in the envelope and putting it in the mailbox, there's nothing stopping you from taking it out later, tearing it up, and going to vote differently in person.
If you took a picture of your ballot, or even if you filmed yourself putting it in the envelope and putting it in the mailbox, there's nothing stopping you from taking it out later, tearing it up, and going to vote differently in person.