Can someone block your I.P. address from their email ?

Someone is sending me messages and I can not respond to them through my email. I have tried to and my email is not delivered. I have also used my sons email and the same delivery notice is sent. I do not know how to block this person and do not want to change my long term email. Is it possible that person has blocked my I.P. address? It is so annoying not to respond to an annoying sender!