As JTP mentions, each email has headers which contain various information. Sometimes, these headers contain each SMTP server that the email went through to arrive at your inbox. Some SMTP servers known as anonymisers remove this information though, and the problem of open relays can mask some originators IPs. That said though, it's worth having a look. In Outlook, right click the email and select Options. At the bottom are the Internet headers. You need this sort of info :
Received: (qmail 18933 invoked from network); 17 May 2007 14:10:56 -0000
Received: from astro.systems.pipex.net (HELO astro.systems.pipex.net) (62.241.163.6)
by server-13.tower-174.messagelabs.com with SMTP; 17 May 2007 14:10:56 -0000
Received: from [127.0.0.1] (81-179-118-78.dsl.pipex.com [81.179.118.78])
by astro.systems.pipex.net (Postfix) with ESMTP id 6870FE0002F0;
Thu, 17 May 2007 15:03:20 +0100 (BST)
The last entry
could could be the address of the originator, and as each country has its own alotted IP ranges, you can hazard a guess based on that. In this case, 81.179.118.78, which, according to
here, is in London, England.