What Are Email Headers? A Comprehensive Guide

What Are Email Headers? A Comprehensive Guide

Emails don’t come without any downside – you may be vulnerable to spam, phishing, and other malicious attacks. To know where those attacks come from, you need to learn about email headers. What is it and in how many ways can it benefit you? Keep reading to learn the answers.

What Exactly Is an Email Header?

An email has two parts – the body (the part where your message is visible) and the header. Now, many people think that an email header is where you can see the subject line, the recipient, and the sender.

They’re not wrong – but it’s just on the surface-level. Actually, an email header contains much more information related to the transmission process of an email – the metadata.

There are many pieces of information contained in metadata such as “from” and “to”, content type, the browser used to write the email, the date of delivery, etc. – more on the metadata in a minute.

To give you a clearer idea of what an email header looks like, take a look at an example below.

An example of email header

How to View An Email Header?

As you can see from the example we have shown earlier, an email header can be extremely long and tricky to understand. Your email client most likely won’t just show it out of the blue – there are a few steps to take before you can access it.

While it may take technical skills to make sense of the information it contains, getting your hands on an email header is not that hard.

Each email client has different steps and we’re going to show you how to view an email header for Gmail, Outlook, Mozilla Thunderbird, and iCloud Mail.

Viewing An Email Header on Gmail

Either you’re on Gmail or Google Apps (such as GSuite), the steps are the same. Follow the instructions below to access an email header on Google products.

  1. Open your Gmail or Google App and click on the email you want to see the header for.
  2. Search for the reply button, click the vertical three-dotted button on the right, and choose Show Original.
  3. You’ll be directed to the overview of the contained information. Scroll down a bit and you’ll find the whole email header, along with the option to download it in .eml (email message) format or copy to clipboard.

Viewing An Email Header on Microsoft Outlook

Due to the many yearly releases of Microsoft Outlook, different versions may have a different approach on how you can view the email header.

However, the steps are not different for the most recent ones (Office 365, 2019, 2016, 2013, and 2010).

  1. Open Microsoft Outlook and double click on the email to access the full message.
  2. Click File -> Properties
  3. You can see a few sections such as Security, Settings, Delivery Option, etc. Scroll down a bit until you see a small scrollable panel containing the email header.
  4. Copy it and paste it to a text editor to see all the information at once.

For Office 2007, the steps are a little bit different. Here is how you do it.

  1. Open the email message that you want to see the header for.
  2. Go to the Message tab, find the Options section, and click the small button on the corner to open a dialog box.
  3. The Message Options dialog will pop out – find the Internet header box and you’ll see the email header.

Viewing an Email Header on Mozilla Thunderbird

You can also access your email header using Mozilla Thunderbird. Follow the steps below to do it.

  1. Open your Mozilla Thunderbird email client.
  2. Double click on the message of your choosing and it will open a new tab.
  3. On the menu bar, click View -> Headers -> All and you’ll see the full email header on top of the message. This is a toggleable option – you’ll keep seeing more information on the header unless you turn it off by selecting View -> Headers -> Normal.

Alternatively, after you open an email, you can also simply press Ctrl + U on your keyboard to view the message source – containing even much more information than the full header.

Viewing an Email Header on iCloud Mail

If you’re an Apple user, you may want to know how to do it on iCloud Mail. The process isn’t that different from other email clients. Take a look at the steps below.

  1. Open iCloud Mail, choose an email and open it by double-clicking.
  2. From the toolbar, click the action symbol that looks like a gear, then select Show Long Headers.
  3. Similar to Mozilla Thunderbird, this is a toggleable action so you can click it one more time if you no longer wish to see the message header.

Understanding The Metadata

If you want further details on the email you receive or send, viewing the metadata is the right course of action. However, you may have to take it with a grain of salt – metadata can still be forged.

That’s right, almost every line (especially the “from” line that shows where the message comes from) is susceptible to forgery – except for Received. In fact, it’s the number one indicator to validate the authenticity of your email.

Received is the line that’s created by your computer, so you should have no problem trusting it completely. It’s also possible for an email header to have multiple Received lines – those lines show you the servers your email travels to until it reaches its final destination.

Also, earlier, we have mentioned a bit about what’s in an email header, right? Below is the list of all the information that the email header includes.

  • From – this is the line that can be forged easily. It contains information on where the message comes from.
  • To – the receiving end of the email (it doesn’t necessarily show the recipient’s email address, though)
  • Subject – think of it as the “title” or the topic that the sender sets on their email.
  • Date – it’s the date and time when an email is written.
  • Return-Path – also known as Reply-To, it contains the address where the reply of that email will be sent to.
  • Envelope-To – it’s kinda similar to Reply-To. It shows that the email was sent to the address on this line.
  • Delivery Date – this is the timestamp when an email client receives the email.
  • Received – this line shows the servers that an email has gone through in order to arrive at the recipient’s mailbox. To read it from a chronological point of view, you must read it from the bottom (where the email was originally sent from) to the top (the final destination of the email or in this case: your computer).
  • DKIM signature and Domain Key signature – DKIM stands for Domain Key Identified Mail. Along with the domain key signature, they both are a part of an email signature identification system.
  • Message-ID – it’s a combination of unique letters and numbers that are created when the email is first written (also forgeable).
  • Mime-versionMIME is an internet standard that extends the format and the functionality of an email. You can attach videos, images, and other files thanks to MIME.
  • Content-type – it tells you whether the email is written as plain text or HTML.
  • X-Spam status – it tells you the score of an email. If it reaches more than the threshold, then the email will be considered spam.
  • X-Spam level – its level depends on the score of the email’s x-spam status. For every point it gains, the x-spam level will show one asterisk.
  • Message body – it’s the main content of your email – the actual message that you want to get across.

Does It All Matter?

You still can use email to boost your efficiency in communication without viewing the email header – so, does it matter whether you know all the metadata or not?

Well, knowing all the information can help you troubleshoot the problems related to your email transmission process. Here below is how you can benefit from an email header.

  • Protect your mailbox from malicious attacks. Despite the convenience that email offers, you still have to guard yourself against phishing (an attack that can steal your sensitive or classified information) and spam.
  • Evaluation purpose. When you ask the technician of your office or email provider for help, they may need to get a hold of your email header. That’s why knowing how to view an email header is important.
  • Email tracking. You can even make use of the data in your email header to track the source of a message by obtaining the sender’s IP address. This is useful if you receive malicious attacks and want to find the identity of the one responsible. The process is also easy – just simply copy your whole email header and paste it on a trace email tool. After you receive the IP address, you can use it to find the sender’s physical location.


Even though most people usually don’t have any reason to view an email header, it has its benefits.

At least, by knowing the use of an email header and how to view it, you won’t be completely blindsided when you suddenly receive a malicious attack in the future. Well, you can’t know for sure, right?

The author

Andrew Vickers

Andrew is a passionate WordPress developer. He loves picking apart source code and learning new things. When he’s not working, Andrew likes to hike and play video games.