You can email someone who has blocked you but he will not receive your email. If someone has blocked you they will not receive your massages at all. You can tell that a person has blocked you if he/she doesn't respond to your messages. If you search for someone while you are logged in and find him, this means he has not blocked you. Learn more on http://www.wikihow.com/Find-Out-Who-Has-Blocked-You-on-Facebook.