Why am I receiving mail sent to someone else?
Although it may seem messages are being indirectly sent to you, in reality you are a victim of spam.
What some spammers do is send a bulk mail to a false or incorrect To address, or occasionally to a real one, while at the same time sending it to masses of people using the Bcc option. What this means is that when the email arrives at your inbox, it looks as though you are receiving someone else's email (because the name which appears is the one name they put in the To field.) So although it may seem that the security of your email has been compromised it has not in reality.
Once you have identified the messages as spam you can block it in your spam filter.