IP Address

how do i know if it is from same machine?

[marie]

I have a list of IP addresses...from hotmail.....the first 4 numbers are the same.......and the rest are different. How do I know if the emails were sent from the same computer?

[bakedjake]

No way to, really, especially if they were on a dynamic dial-up.

[lukasz]

And even if there is only one IP you still cannot determine if it is the same computer. My ISP uses proxy server and all of my computers appear in log file as one IP.

User agent may help a bit in figuring it out.

[jdMorgan]

If a legal problem or criminal activity is at issue in this case, law enforcement can subpoena the ISP's records to narrow down the possible users of a given IP address at a given time. This info may be useless to you, but just in case...

Jim

[chris_jt]

The information isn't entirely useless. In the case of suspected criminal activity, you can also open a complaint with the FCC and US Secret Service. Visit their website for more information. In support of the moderator's reply, you can check with your local law enforcement and find out if they have a "computer crime" division. If so, they should be able to provide you with guidance on how to report suspected criminal activity. Taking such proactive measures can have an additional benefit of providing proof of your service's conduct should it come into question.
As another approach, there are components out there that can be used to perform dynamic reverse lookups on domains and IP's to check their validity. Specific components, however, are subject to the type of technology being used and also subject to your host provider's willingness to support them. Check with your hosting partner for more information.
In the case of emails, we use a component which checks the validity of the sender's domain. The component also checks the ability of the email address to receive emails to ensure the submitter is providing a valid email address. In addition, we also provide a publicly accessible "No Spam" policy.