Whenever an email is sent, information is transmitted with that email and the route the email takes across a network is recorded. This information is known as the ‘Extended Header’.
The extended header can be of great use to the researcher and when used correctly, provides an insight into the sender, their software and hardware and potential recipients.
The extended header information potentially includes the senders IP address, email client, return address and the route the email has taken to reach its destination. This is useful in identifying and investigating ‘spoof’ or ‘phishing’ emails.
There are three main issues to discuss here before we move on.
The first is that different email services provide different information in the extended header.
The second is that we need to be in possession of original email, not one that has been forwarded to us for examination. A forwarded email will contain extended header information of the forwarder, not of the original email. The subject email can in some circumstances be sent as an attachment and in this case the extender header information will be retained.
The third is that different email clients / web based services present the extended header in different formats and the information is accessed in different ways. A Google search will reveal how to view the extended header information in your email client or web based service.
For our example, we are going to use an email sent from Microsoft Outlook 2013 to a gmail.com address.
We will be viewing the extended header of the email thorough the web based gmail service, but similar procedures apply to all email clients and services.
Below are the details of the email as it was sent from the Outlook 2013 account. We can see details of the recipient, the CC recipient, the BCC recipient, the email subject and the details of the attachment.
So, heres how to view the extended header information in the gmail web service:
- Log in to the web service at mail.google.com
- Open the email in question
- Click the drop-down arrow to the right of the reply button
- Click on ‘Show Original’ in the menu that has appeared
- The extended header information for that email will open in a new window
- Select all of the text that appears and copy it to your clipboard
- Open either Word, Notepad or a similar text editor and paste in the extended email header. You can examine the header in its web page but I find it easier in an editor
For the extended header information used in this example , click on the icon below. It should open in a new tab.
This example has the relevant sections highlighted. The red numbers on the highlighted section do not form part of the header and have been appended for reference only.
To examine an Extended Email Header, we should read from the bottom up.
So, working upwards, here are the details:
1. The text content of the email
2. ‘Disposition-Notification-To’ means that the sender has asked for a delivery or read receipt form the recipient. This receipt is often sent automatically when the recipient receives or opens the message, but this option can usually be modified in the recipients email program or client giving the recipient the option whether to send a receipt or not.
3. X-Mailer is the email client used by the sender. A Google search for ‘Microsoft Outlook 15.0’ identifies the client in this case as Microsoft Outlook 2013, so the sender must be running Windows.
3A. Message ID is the unique ID refernence of this message. It may be generated by the mail server or the ISP, but is unique and essential when speaking with administrators to trace a message and related information on a server or network.
4. The day, date and time sent from the senders machine. In this case its GMT +0100 as it is summer. Look closely, further up the header (below item 10) and you will see the server time (kundenserver.de) is GMT +0200 as that is the local time.
5. The subject line of the original email
6. The ‘CC’ or Carbon Copy recipients email address (email@example.com).
NOTE: the ‘BCC’ or Blind Carbon Copy recipients name or email address (firstname.lastname@example.org) is not shown in the header.
7. The main recipients email address
8. The email address from which the original email was sent.
9. The reply to address (email@example.com) which is different to the senders email address. When the recipient replies to the email, this is the email address the reply is sent to. In this case this is the original senders email address, but could be an alternative email address. This is often the case in ‘scam’ emails.
10. This is the hostname of the computer used by the sender (jonmbp)and the senders public facing Internet Protocol (IP) address. In this case this IP address 126.96.36.199 when investigated (type it in to centralops.net) appears to be owned by Rapidswitch Limited in the UK.
Reading upwards, the first IP address that appears is usually that of the sender.
NOTE: not all email service providers capture the senders IP address in the Extended Header.
11. This entry confirms that the email was delivered to firstname.lastname@example.org and this is the recipients email address that this header relates to. This would be different if we where to examine the header of the other recipients email addresses.
The time and date of delivery to the server are shown. In this case the time is followed by the letters PDT which refer to ‘Pacific Daylight Time) and -0700 which means the time displayed is PDT minus 7 hours. This is not the time the email was read by the recipient.
Take particular care when interpreting times in Headers as they are specific to the location of the mail servers.
For help finding the Extended Email Header in your particular service or client, check out Header Help
As can be seen from the above example, Extended Email Headers provide a wealth of information about the originator and the content of an email, its path and recipients.