I had a situation like this a few years ago and I handled it the way several PPs have suggested. My parents were longtime friends with John. My mother has email, my father does not. John would email my mother's email address to send them jokes or political rants. Somehow, he got a hold of my email address. I was working a ton and was getting about 300 emails a day at work, and at home and didn't want any extra emails. For some reason, I'd get email jokes or political rants from him. An added bonus is that I don't agree with him on many political topics so I'd get irritated reading them, too.
I replied to him and asked him why he was sending these things to me. I mentioned, politely, that I already got too many emails a day and requested to all of my friends that they not send me jokes or political things. He replied that he was writing to me because for some reason, my mother wasn't getting his emails. As if his jokes were of the utmost importance. No one else I knew had trouble sending my mother email. Her email provider was reliable. He was requesting that I forward them to her, even though I could see her email address on his "To:" line.
Several times, I forwarded them to her and replied to him with her correct email address. He continued. Several times, I told him that I just didn't have time for more jokes, or to be forwarding things for him. He continued. Several times, I replied to both him and my mom with her correct email address. He continued.
I was in your position. I finally just blocked his email address from my account. That was it. I said no more. I saw him at other family events and he never said anything about it. I don't know what happened. About a year later, I upgraded my computer, so I had the same email address but a new version of MS Outlook and no filter blocking his email address. I never got any more emails from him.
So he learned his lesson through my actions, because he wasn't listening to my words. I still don't know why he was sending things to me. I don't know if he wanted to convert me to his political viewpoints or what was going on. But my method was effective.
Mainly, I was insulted that he was blatantly disrespecting my requests. He was disrespecting my time, abusing my politeness, and misusing my assets (my email and bandwidth) and none of it was respectful. That's why I finally just blocked him. I found him to be rude, in that way, and I wasn't going to try to find the good, or give him the benefit of the doubt any longer.