I have Hotmail and I’ve been getting nasty e-mails from somebody who I do
not know. I figured out how to view the headers and try trace the IP addresses.
As I was doing some trial and error from the X-Originating-IP addresses from
people on my list, I noticed that one of my friends has the EXACT same
X-Originating-IP address from the one I’ve been getting my nasty e-mails from.
Is my old friend sending me nasty e-mails off of the same computer but through
different e-mails? If it helps, there both Hotmail accounts. Thank you in
advance for your help and assistance.
Of course he could be, but the IP address doesn’t prove it.
There are several reasons that a single IP address could be used by several
Become a Patron of Ask Leo! and go ad-free!
In the simplest case, an IP address uniquely identifies your computer on the
internet. However for many reasons that’s becoming less and less common as
An IP address only identifies whatever it is you have connected to the
internet. In many cases these days, that’s a router:
In a case such as this, all the computers to the left of the router will
appear on the internet as having the same IP address. That IP address is
actually assigned to the router, and it handles routing the traffic to the
appropriate computer on the local network.
In a case like this the IP address you’ve extracted from your email headers
may get you as far as the router, but that’s it. You can’t tell which computer
behind the router was responsible for it.
The diagram above is a common home or small business configuration. It’s
important to realize, though, that in larger installations there could easily
be hundreds of computers sharing a single or smaller set of IP addresses. Once
again, with just the internet IP address, there’s no way to tell which computer
sent your email.
Dynamic IP Addresses
Many computers are connected to the internet using what’s called a “dynamic”
IP address. The IP address is assigned to that computer when it first connects
to the internet, and is released when it disconnects. A common example is
dial-up connectivity where the connection and disconnection are both obvious
and frequent. Persistent connections can also use dynamic IP addresses, and in
fact can be re-assigned a new address even without having to disconnect –
though typically that’s not the case. However even the slightest disconnection
could cause a new IP address to be assigned.
hundreds of computers sharing a single or smaller set of IP addresses.”
What’s important to note here is that the IP address you were assigned
yesterday might very well be used by someone else today.
That means if your sender is using a dynamic IP address, then it might be
someone else entirely if you see that same IP address in another email at a
later time. There’s no obvious way to know.
Local IP addresses
If the address you see begins with 192.168., 172.16. through 172.32. or 10.
then it’s not an internet IP address at all, but rather a local IP address
assigned by a router.
Looking at the diagram above again, you can see that internet IP addresses
are assigned to the router’s connection to the internet. However on the left,
on the local side of the router, the addresses are assigned from a range of IPs
reserved for local networks. Most home and small business routers assign from
the 192.168. address range.
The problem here is that if that’s the IP address you’re seeing, then it
tells you pretty much nothing. There are probably tens of thousands of machines
with that 192.168.?.? IP address, scattered on local networks around the
Without the internet IP address, there’s just no way to get
The Bottom Line
Ultimately, as I’ve said time and time again, trying to use IP addresses to
locate someone is futile for the average person. Yes, technically there may be
ways to backtrack, but it’s complex, and often involves breaching privacy
barriers that will require law enforcement and/or court orders.
16 comments on “Does email coming from the same IP address imply that it was the same computer?”
I’m in a battle of the bands compitition where the winner is judged by the amount of votes they get on line. You can vote once a day from your computer. They count your IP address. I’m worried that if an office of 40 friends all vote for me, they only count as one vote if it’s the same IP address. 40 different computers, 40 people voting, one vote counted. Can this happen?
Yes, it could.
The crucial point in this case is that it’s being sent from Hotmail. Any emails sent through a web-based service will have the webmail provider’s email address as the X-Originating-IP because the actual computer used to send the message is not writing the headers. The headers will be written by the server-side script on the Webmail hosting providers service.
So any email sent from a webmail service will have one of the IP addresses that resolves back to the webmail provider, and all you can deduce from it is that the spammer was connected to the same webmail server as your friend on hotmail.
—–BEGIN PGP SIGNED MESSAGE—–
Actually, HotMail does occasionally include IP address of the computer
accessing the web service as the x-Originating-IP – I just confirmed it.
Not sure about other providers, but that bit of anonymity obviously
—–BEGIN PGP SIGNATURE—–
Version: GnuPG v1.4.6 (MingW32)
—–END PGP SIGNATURE—–
Yes…hotmail does include at least the IP address of the router that the user was connected too, I have confirmed that when i send an email through hotmail it includes my routers IP every time without fail.
It is possible your friend sent the mails but you cant be sure, what you could do is check all the IP’s of your friend and also from the person sending the malicious emails and see if there is any pattern.
I’m having the exact same issue. I’ve compared the malicious emails with the other emails and found that one of the IPs found in both email addresses headers is EXACTLY the same (starts with 10. and the rest of the numbers match identically). Does this prove anything?
Hi Leo – your site and info has been most helpful. I think I have the answer but hopefully you can help. I have had a number of e-mail from two different people supposedly, but both mails have come from IP 86.178.233.xxx. Identical. These emails have come to me over a period of about 2 weeks. These MUST be coming from the same computer, or router. Am I right? So one e-mail couldn’t be coming from Aberdeen, and one from London.
I am getting abuse emails showing my close friends Static IP address.. But i gotta doubt on my new roomate. Is it possible for my roomate to use my Friend’s static IP and send abuse emails to me using our common internet connection.
[Note: we use same internet connection and same computer for internet perpose..]
Pls help me with the solution… thanks!
My email was compromised and I am sure it was my sister in law. I checked the IP who logged in my account and was 188.8.131.52 and her emails come from IP which is 184.108.40.206. How can I prove that to Immigration office? Please advice. She is ruining my immigration. Please advice. Thank you very much.
That is more a question for a lawyer with experience in IT cases, than a tech website with no expertise in legal matters, unless there is a lawyer out there who chooses to weigh in.
I have constantly received emails from 2 different people with same IP address starting 209…Does this mean its the same person.
In this case, it’s likely that they are the same, or at least from the same house, company, Internet café, or library.
I would NOT say likely at all.
Answered in the article. Please read it.
Emails With same IP address does this mean they are from same location
In most cases, no. Because consumer IP numbers are assigned randomly by the ISP whenever a customer logs in.