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IP addresses can change for many reasons; you can't absolutely rely on them to give location.

Hi, Leo. I don't know if this is something you can answer or not, but I need to know because I'm in quite a sticky situation. Does email coming from the same IP address imply that even if it's not the same computer it's definitely in the same country? It's impossible for a friend of mine in one country to have the same IP address as someone else in a completely different continent? Right?

In this excerpt from Answercast #14, I talk about how IP addresses identify the location of computers and how it might not be exactly what you expect.

Are country IP addresses always different?

No.

So, there are two different ways that this can happen.

  • One, is a multi-country ISP.

There aren't that many, but it's possible. An ISP could certainly reuse IP addresses and reassign them to different users as they login. That's what DHCP does: the dynamic protocol that assigns an IP address to you when you connect your computer.

Typically, yes, they're all in the same country. But I could certainly envision an IP or ISP that services more than one country. Since we don't know what country you're talking about, I can't say for sure that this isn't the case.

You did say, "Definitely." And I can't say definitely.

  • Two, is Proxy Servers

The other scenario is one that's slightly more likely and that is proxy servers.

If you send email through a proxy server of some sort (or if you use a web mail service of some sort), then the IP address that is in the email could well be that of the proxy service (or of the web mail service) and not the IP address of the physical location of the computer from which the person is sending email.

IP address location is not definite

So, there are scenarios there where the IP address associated with the email:

  • Not only isn't necessarily in the right country
  • But it's not even associated with that user in any way; in any direct way.

So, in absolute terms, No. We cannot infer that 'absolutely' the same IP address means the same country. There's definitely a lot more information that's needed before you can even come close to saying what's really going on here.

In general, sure, it's likely: it's common. It is most often the case that the IP address does infer a specific country.

But, in absolute terms, there are ways around that, and ways that you cannot count on being used, or not being used, to obfuscate exactly where somebody resides.

Article C5292 - May 3, 2012 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

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