How do you know if your email message has been blocked or if your server was unable to locate the address?

I sent out an email and it was returned. I don't know if the person blocked my email or the server was unable to make a connection.

How do you know if your email message has been blocked or if your server was unable to locate the address?
If the mail bounced back to you, it was because the servers could not reach the intended address. If you've been blocked, there is no notification of it and it isn't bounced back.