E-mail is one of the most popular services on Internet, but traditional e-mail system is transmitted in plain text, which brings a lot of security risks. In order to ensure the security of e-mail, this paper analyses the integrity, confidentiality and repudiation of information. It introduces the protocol of e-mail transmission and encryption algorithms. Through the comparison of the algorithms, it presents an encryption and signature scheme based on triple DES and Elliptic Curve Cryptography, and designs a fast algorithm of ECC. Finally, it sets up a secure and efficient e-mail system, which implements message encryption, digital signature and identification effectively in the process of electronic mail transmission.