The following is a normal EMail message coming from a dial-in user via their ISP.
Received: from out5.ibm.net (220.127.116.11) by Your POP/SMTP Server's Address with SMTP (Eudora Internet Mail Server 1.2); Sun, 22 Feb 1998 02:06:20 -0500 Received: from brow529 (slip-32-100-191-102.ca.us.ibm.net [18.104.22.168]) by out5.ibm.net (8.8.5/8.6.9) with SMTP id HAA13524 for Valid EMail Address Withheld; Sun, 22 Feb 1998 07:06:15 GMT Message-ID: <34EFCDE8.7BB9@ibm.net> Date: Sat, 21 Feb 1998 23:04:08 -0800 From: Valid EMail Address Withheld X-Mailer: Mozilla 3.0 (Win95; I) MIME-Version: 1.0 To: Valid EMail Address Withheld Subject: pictures Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit
In this case, you can see that a dial-in account on ibm.net (brow529 (slip-32-100-191-102.ca.us.ibm.net [22.214.171.124])) sent mail to out5.ibm.net (126.96.36.199) and then on to your Post Office.
Also, notice Message-ID contains the sender's domain, ibm.net.
Additionally, From contains the EMail Address of who sent the EMail.
The following is a normal EMail message coming from a dial-in user via their ISP. Notice that it is slightly different than the previous example.
The routing headers define the routing of the EMail message from Post Office to Post Office. If you look at the IP Addresses, you can see how the mesage travelled through the net. Other information is also provided message headers that provide information about the location of sender.
In this case, you can see that a dial-in account on pobox.com (pobox.com ("port 2770"@[188.8.131.52])) sent mail to bos1c.delphi.com (184.108.40.206) and then on to your Post Office. Notice that the way a dial-up is described here is different than that ofibm.net. Dial-up IP Addresses, are described in many different ways in EMail headers. Start learning buy looking at the headers from your friends.
Also, notice Message-ID and ESMTP id contains the sender's domain, ibm.net.
Additionally, From, Errors-To and Reply-To contains sender's domain and address. Further, this header contains Organization which provides you with some more information about the sender.