E-mail hackers use many methods in their work, in this paper, most of such efficient methods are demonstrated and compared. Different methods and stages of such methods are listed here, in order to reveal such methods and to take care of them but the most common discussed method in this paper is SQL method. SQL injection is a type of security exploit in which the attacker adds SQL statements through a web application's input fields or hidden parameters to gain access to resources or make changes to data. It is found that the SQL is an efficient way in preventing E-mail hacking and its efficiency reaches about 80%. The method of SQL injection can be considered as an efficient way comparing with other methods.