Question about unique IP's

[Quarky]

I have always thought that everyones public IP-address was always unique, being either a static IP-address that is always the same, or a dynamic IP-address that you get from your Internet-provider that can change...

But now I confronted someone in the UK about an email he send to me. In the headers of the email, I can see the IP from which the mail was send, like this (I x-ed part of the IP-address for privacy):

Received: from [80.195.xxx.xx] (helo=HP70261839619)
by asmtp-out1.blueyonder.co.uk with smtp (Exim 4.52)
id 1J90zW-0002xV-IZ
for myname@myprovider.nl; Sun, 30 Dec 2007 16:26:23 +0000

Over an extended period of time, I have received emails from this person, always with the same IP-address: 80.195.xxx.xx.

With this person I had some discussion about IP-addresses and how you (or the internet-provider) can trace back where traffic came from. But he is stating the following:

"...The cable IP address is for the junction box which serves about 30 households..."

This surprised me, because I always thought public-IP's where unique, but if the above is true, his neighbour is using the same IP...

Anybody who knows more about this?

[Jason09]

It might be the same public default gateway address obtained from the ISP. Otherwise, you are correct, every public IP address connection from the ISP will be different for people. Or, if someone releases their IP, someone else may get it.