E-mail isn't just a simple way of delivering information, but is a core tool of task process. A company mainly uses e-mail as a way to internally communicate and to process main tasks of business. Currently, mail capacity being used in a company has been increasing in rate of 40% and 70% of company information is being preserved in e-mail. However, most of the companies manage e-mail by using diverse mail client programs in personal PC. It is difficult for investigators to select mails important for investigation in environment of wide and diverse mail client environments during investigation. In this paper, large-capacity mail file produced by diverse mail clients is analyzed, and tool independent from e-mail file format and still capable of performing analysis is proposed and designed.