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Editorial Team
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Asked: 2026-05-24T05:38:34+00:00

I’m building a email app (a web app which you interact with almost exclusively

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I’m building a email app (a web app which you interact with almost exclusively by email) and I’d like to be able to take a reasonable guess as to where my users are from using only their email headers. (I’m a firm believer that ‘defaults’ in web services should be as intelligent as possible!)

Does anyone with decent knowledge of modern email routing (ie. super-providers like google, yahoo etc) have any good ideas as to how to pull a user’s country from an email with a reasonable amount of accuracy and, if possible, a rough indication of how accurate this would be, so I can disregard the guess if it’s unlikely to be correct?

Ideas so far:

  • Timezone (nowhere near accurate enough, but useful)
  • email domain TLD (not very reliable, I have a .com TLD and I’m British)
  • GeoIP of IPs in email header (not really sure whether this would work, which header would be the most reliable?)

Thanks for your head-cycles!

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1 Answer

  1. Editorial Team

    “normal” mail

    I once wrote a thunderbird plugin which does the same and it exclusively used the top level domains to display the station of each route. A lesson learned there is that the mail may go over 10 or more servers until it reaches the recipient. You have to use the first route entry:

    Received: by mail.cweiske.de (Postfix, from userid 65534)
    id 1DB83119102DA; Sat, 30 Jul 2011 13:58:30 +0200 (CEST)
Received: from fmmailgate02.web.de (fmmailgate02.web.de [217.72.192.227])
    by mail.cweiske.de (Postfix) with ESMTP id D56F6119102D3
    for <me@example.orge>; Sat, 30 Jul 2011 13:58:18 +0200 (CEST)
Received: from smtp03.web.de  ( [172.20.0.65])
    by fmmailgate02.web.de (Postfix) with ESMTP id E54B11A74B6A1
    for <me@example.org>; Sat, 30 Jul 2011 13:57:52 +0200 (CEST)
Received: from [84.185.130.22] (helo=[192.168.178.21])
    by smtp03.web.de with asmtp (WEB.DE 4.110 #2)
    id 1Qn88O-0006jw-00
    for me@example.org; Sat, 30 Jul 2011 13:55:14 +0200

    In that case, the sender is 84.185.130.22 – a whois on that IP gives us (correctly) Germany as the source of the mail.

    Another example, first entry only:

    Received: from carnot.localnet (ip-118-90-104-106.xdsl.xnet.co.nz
[118.90.104.106])
by ananke.wxnz.net (Postfix) with ESMTP id D758D17002B
for <me@lists.sourceforge.net>;
Sun, 31 Jul 2011 10:08:57 +1200 (NZST)

    which even contains .nz as resolved hostname – this time correctly New Zealand. whois also gives you new zealand.

    webmail

    You’d have to check if mails from i.e. gmail web interface also contain the correct IP, which I doubt. An example from gmail:

    Received: from mail-wy0-f179.google.com (mail-wy0-f179.google.com [74.125.82.179])
    by mail.cweiske.de (Postfix) with ESMTP id A739A11910543
    for <me@example.org>; Wed, 23 Jun 2010 23:05:42 +0200 (CEST)
Received: by wyb38 with SMTP id 38so1740851wyb.24
        for <me@example.org>; Wed, 23 Jun 2010 14:05:42 -0700 (PDT)

    The sender IP is totally missing here, and the only information you get is the IP from google’s mail server. The time zone there is also the zone of the server, not the client’s time zone – it would be +02:00.

    conclusion

    In the end, no signal gives you 100% accuracy and you have to employ all of them.
    Also, every single bit in an email may be forged – don’t forget that.

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