The singer – who was appearing with her fellow American Idol judges Keith Urban and Harry Connick Jr – welled up while speaking about the message from her little boy.
"It just made my life. It says, I'll luv you beyond forever Mom," she read. "I'll cry right now! Stop it! Oh my god!"
She went on, "Beyond forever. That's the line, that's it. You know, I came home and it was on my bed and then I opened it and just left it there…
"(It was) in a big manila envelope, a yellow envelope, and it said, 'To: Mom, From: Max.' And I opened it, and I was like, 'Oh my god'."
"He's a poet!" Ellen said. "He's a genius," Jennifer replied. "Come on, let's be honest."
"That's amazing," singer Harry added. "I get notes from my kids, but it's like, 'I'll love you as long as you want if you give me a hundred dollars. All this 'beyond forever' stuff – you live in some kind of fantasy world, Jennifer Lopez!"