Based on a non-repudiation protocol NRPUM, which provides point-to-point non-repudiation services, this paper proposes a non-repudiation solution to secure email systems. Specifically, non-repudiation evidence is used at every hop between relay nodes so that an evidence chain is formed between end hosts. An email non-repudiation delivery system is then developed based on this concept. Our experiment results show that the solution is feasible and the system is effective.