Email Headers contain all the information about where an email has been; how many computers it has been routed through; and more.
This information is easy to access but not often (cybersecurity outfits will use it along w/ other methods to track down spam and spammers). We can use email Header info to see if something like a web proxy or IP distorter is used, or just to see if the IP address listed matches that of it’s purported sender.
Google Mail (Gmail):
1) Open the email you want to examine.
— Yahoo! Mail: select “View Full Headers”, or “View Headers.”
— Windows Live Hotmail (this does not work w/ Safari or Mac OS…):
Select “View Source”. A window opens displaying the full header as well as the HTML source of the email message.
Desktop Email Clients:
Typically the option for viewing the full email header w/ desktop email clients like Outlook and Thunderbird are found in their drop-down menus.