I've been asked many times over the years how to actually get at the email headers when using a standard email client to read messages. This not only comes in very handy when you're troubleshooting deliverability problems on the sender's side (IP address, HELO values, authentication, etc.) but also allows you to take a closer look at the individual ISPs and what information they tack on to the message headers which can usually tell you something you didn't know before. Headers are an immutable piece of data that represent the snapshot of when and how the email was sent from points A to B. Granted, if you work in deliverability to any extent, this is child's play.
However, if you've ever wanted to be an email diagnostician (I remember saying this on my 5th birthday!) or found yourself wondering what people meant when they discussed email headers, keep reading and I'll show you some of the most popular email clients' paths to headers. Keep in mind, every email that is successfully sent contains headers. But, the programs that consume the email packets and present them to the end recipients vary on how transparent they are with exposing headers. Following the lead of the major clients below, you'll get a pretty good idea of what access strategy to use in the majority of email clients available.
Windows Live Mail (desktop client):
Windows Live Hotmail (web client):
*If left clicking doesn't produce what's shown in the image, right click.
Hopefully this gives you a better idea of where to look when trying to needle out the email headers from your email client without having to get too technical with setting up your own fancy inbound mail server or handler. If you have any questions, let me know and I'll be glad to go deeper. Many resources are available explaining the value of and how to read headers. Depending on the feedback, I might post a follow up to this explaining what you should look for and how the data points play into enhancing your deliverability strategy. Let me know what you think!