E-mail service is one of the most important internet services. E-mail security protocols are used to provide security services for email systems. It includes confidentiality, authentication, message integrity, non-repudiation. Pretty Good Privacy (PGP) and Secure/Multipurpose Internet Mail Extension (S/MIME) are commonly used email security protocols. The used algorithms in PGP suffer from several problems. The large prime numbers is considered a big problem in public key cryptosystem. The chaotic public key cryptosystem is new trend in cryptography. In this paper a new public key cryptosystem based on chaotic system is introduced. The provided cryptosystem is based on three maps of betatransformation mapping. The proposed cryptosystem has been used to provide the public key features such as key-exchange, chaotic key management system and encryption/decryption. The new chaotic key exchange protocol is evaluated against the Diffie-Hellman elliptic curve cryptosystem (DHECC). The proposed technique is integrated with the PGP protocol, it is developed using open source bccrypto-net-1.7 project, C#.net programming language and
open source for OpenPGP. The test results show that the proposed cryptosystem improved both the security and performance.