The Beatles legend said in a clip on his website that anything he receives after October 20 will be "tossed".
"This is a serious message to everybody watching my update. Peace and love. Peace and love," he said.
"I want to tell you after October 20, please do not send fan mail to any address you have. Nothing will be signed after October 20. If that is the date on the envelope, it’s gonna be tossed."
The rocker said the warning was being made with "peace and love", adding that he is too busy. "So no more fan mail. Thank you, thank you. And no objects to be signed. Nothing," he said.
Earlier this year, Liverpool residents beheaded a statue of the musician after he made dismissive remarks about his home city.