Yes it is very easy for anybody to block an email address on their email account. This is done all the time to keep spam out but can also be used to filter the emails of certain individuals or addresses. In most cases there is no way to know if an email has been blocked. Most email hosts will just reroute a blocked email address to the user's trash folder so it is never seen. Please let me know if you need further clarification or have other questions. Thanks!
I'm sorry you were not satisfied with the answer you got. As I said in both my response and my signature, please "reply" if you need more information or further clarification. You were not obligated in any way to accept my answer if you were not satisfied. Leaving negative feedback was unnecessary and severely affects my scores.