To trace an email, you'll need to locate the email header that came with the email. Every email has an email header and message body. An email may be going through a number of hops, and a header is appended with the IP address of the email server processing the email. When an email reaches the final destination, your email provider appends its IP address to the header.

With ever growing number of spam emails flooding the Internet, more and more ISPs tighten their email filtering system to prevent spams delivered to their clients. It is virtually impossible to block even 50% of the spams arriving in a mail server, and there will always be false positives (legitimate emails filtered as spams). In an effort to reduce spam emails, the Federal Trade Commision (FTC) passed the CAN-SPAM Act of 2003, but the Internet spam traffic is still on the rise.