Federal law strictly limits the information that online service providers like Yahoo! may disclose about their users. However, the email message itself contains some information relating to the sender's identity. In the headers of email messages sent via Yahoo! Mail, an Internet Protocol (IP) address that corresponds to the sender's Internet service provider (ISP) is included.

To view a full header, click Full Headers in the lower-right corner of the page. A new window opens with the same message, but now also shows all the header information for that message at the top. See it? It’s got tons of computer gobbledygook, but it also has some information you can use.

You should be able to find a line that contains an 8 to 12 digit number, separated by periods. It might look something like this:

Received: from [123.456.78.91] by...

The "123.456.78.91" represents the unique IP address of the sender's ISP. Once you identify the IP address, you can run a "whois" search to determine which ISP provides this person with Internet access. If there’s more than one Received: line, read them from top to bottom (the topmost is the most recent.)

There are several utilities available on the web to run a whois search. Here's one web site that can help you to determine which service provider is responsible for the IP address.

If the spam or abusive email is being sent from a Yahoo! Mail account and you are not using Yahoo! Mail, please forward an unedited copy of the message with full headers here.

We’ll evaluate the situation and take action per our Terms of Service. Spamming from a Yahoo! Mail account is not acceptable.