You shouldn't open someone else's mailbox.
Todd was waiting for a new credit card in the mail, but he didn't receive it.
Todd wants to check if his neighbors received his mail instead.
Todd asks his neighbors if they happened to receive any mail that was for him.
Todd looks in his neighbor's mailbox without asking and goes through their mail.
Todd's neighbors think that he is polite, and Todd is able to find out if they received his mail.
Todd is invading people's privacy and could be in trouble if they find out.