Electronic mail (E-mail) spam is today's popular problem for users and the service providers. Spammers not only send a large number of emails but also use the spamming techniques to spoof the secret information of users. They force the users to draw their attention to read. In this paper, the authors propose an online spam filter for duplicate or near duplicate message content detection scheme. This efficient scheme uses strong signature technique to detect duplicate message with matching percentage that helps user to decide the slender modification in e-mail spam.