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What Is an Email Header and How to Use It (2021 Guide)

what is an email header

Curious about what an email header is? 

An email header is the part of an email that contains information about the mail’s sender, receiver, and subject. The header also includes more technical information for efficient email delivery.

In this article, I’ll cover everything you need to know about email headers, including what a header is and why it’s essential. I’ll also show you how to view your complete email header and how to create perfect pre-header text.

This Article Contains:

Let’s get started.

What is an Email Header?

The header (internet header) is the section of your email that includes information like the sender’s details, receiver’s details, subject, and date.

Other technical details like the Return Path, Reply-To Field, and Message ID are also included in an email header (more on these later in the article).

Here’s what a complete email header looks like:

What is An Email Header

But wait…don’t headers refer just to the top of the email?

In most documents, a header generally refers to the top of the page.

However, email headers don’t function in the same way.

Email headers are specialized pieces of information that contain data that’s vital to the email’s delivery. And while some aspects of the email header can be found at the top of your email, your header needs to be accessed separately.

So what is the start of the email called?

The information at the start of an email message is called the pre-header text.

What Is the Pre-Header Text?

Your pre-header text refers to the lines of text mentioned after your subject line in your inbox. Strong pre-header text can go a long way in getting recipients to open your emails.

Here’s what I’m talking about:

What is An Email Header - What Is The Pre-Header Text

What Are the Different Aspects of an Email Header?

Let’s take a look at the technical aspects of an email header and what they mean:

  1. From
  2. To
  3. Date
  4. Subject
  5. Return-Path
  6. Domain Key and DKIM Signatures
  7. Message-ID
  8. MIME-Version
  9. Received
  10. X-Spam Status

And here’s where each aspect is located in an email header:

What is An Email Header - Different Aspects Of An Email Header

Let’s break each element down:

1. From

The From field indicates the sender’s name and email address.

2. To

This field contains the email’s receiver’s details.

It includes their name and their email address. Fields like CC (carbon copy) and BCC (blind carbon copy) also fall under this category as they all include details of your recipients.

If you want to find out more about carbon copy and blind carbon copy, check out how to use CC and BCC.

3. Date

This is the timestamp that shows when the email was sent.

In Gmail, it usually follows the format of “day dd month yyyy hh:mm:ss.” 

So if an email had been sent on the 16th of December, 2020, at 4:57:23 PM, it would show as Wed, 16 Dec 2020 16:57:23.

4. Subject

The Subject mentions the topic of the email.

It summarizes the content in the message body.

5. Return-Path

This mail header field is also known as Reply-To.

If you reply to an email, it will go to the address mentioned in the Return-Path field.

6. Domain Key and DKIM Signatures

The Domain Key and Domain Key Identified Mail (DKIM) are email signatures that help email service providers identify and authenticate your emails.

7. Message-ID

The Message ID is a unique combination of letters and numbers that identifies each email. No two emails will have the same Message ID.

8. MIME-Version

Multipurpose Internet Mail Extensions (MIME) is an internet standard that converts non-text content like images, videos, and other attachments into text so they can be attached to an email.

9. Received

The Received field lists all the servers that an email went through before arriving in the recipient’s inbox. It’s listed in a reverse chronological order — where the server on the top is the last server the email message went through, and the bottom is where the email originated.

10. X-Spam Status

The X-Spam Status shows you the spam score of an email message.

First, it’ll highlight if a message is classified as spam.

Then, the spam score of the email is shown, as well as the spam threshold for the email.

An email can either meet an inbox’s spam threshold or exceed it. If it’s too spammy and exceeds the threshold, it will automatically be classified as spam and sent to the spam folder.

How to Access Your Email Header

Here’s a step-by-step look at how you can view a complete email header in Gmail and Microsoft Outlook:

1. How to View the Full Email Header in Gmail

Here’s how you can view your email header in Gmail:

Step 1

Click and open the email for which you want to see the header.

What is An Email Header - How To Access Your Email Header in Gmail

Step 2

Click on the three dots What is An Email Header - How To Access Your Email Header in Gmail next to the Reply button What is An Email Header - How To Access Your Email Header in Gmail.

What is An Email Header - How To Access Your Email Header in Gmail

Then click on Show Original in the drop-down menu.

What is An Email Header - How To Access Your Email Header in Gmail

Step 3

The email header will display in a new window.

It will show some header field details like authentication results, DKIM signature, and the MIME-version.

If you want to download the full header with the rest of the data, click on Download Original.

What is An Email Header - How To Access Your Email Header in Gmail

2. How to View the Full Email Header in Microsoft Outlook

Here’s how you can view your email header in Microsoft Outlook:

Step 1

Click and open the email for which you want to view header details.

What is An Email Header - View Full Email Header in Outlook

It will open in a new window.

What is An Email Header - View Full Email Header in Outlook

Step 2

Click on File, situated right next to the message tab.

Then, click on Properties at the bottom of the window.

What is An Email Header - View Full Email Header in Outlook

You can find the header information in the “Internet headers” section of the dialog box.

What is An Email Header - View Full Email Header in Outlook

Why Do You Need an Email Header?

Here are a few reasons why email headers are essential:

1. Email Headers Protect Against Spam

The header contains several information fields that help email service providers (ESPs) identify an email. ESPs analyze the header information to determine the email’s legitimacy and whether it should be delivered to the intended recipient.

These protocols protect your mail account and personal data from phishing attacks and spam emails.

2.  The Message Header Clarifies Sender/Receiver Information

Every email header contains the From and To fields. There’s also the Subject field and Date indicator, highlighting the time and date when the email was sent.

Without this information, you wouldn’t be able to identify the email’s sender or receivers, which help you determine if it’s legitimate.

3. Email Headers Help You Track an Email’s Route

When a user sends an email, it originates in a sending server and travels through several Mail Transfer Agents (MTAs) before reaching the intended recipient.

When an email passes through an MTA, it’s automatically “stamped” by the server with header lines like the recipient, date, and time of the email.

This header information can help the recipient track the email route — allowing them to check all the MTAs the email passed through to arrive at its destination. This is useful when you’re trying to view message source details and physically track down the origin of malicious emails.

But that’s not all.

If you expand the email header, you can even obtain the sender’s IP address to track the message source further.

How to Design Great Pre-Header Text

Although most aspects of an email header are technical and can’t be changed, the pre-header text can be customized to be more appealing to readers.

But how do you create an attractive pre-header text that retains the reader’s interest?

Here are four key tips:

1. Emphasize Your Brand

The pre-header text is one of the first things readers see when they open their inbox. If your pre-header text doesn’t showcase your brand, your mail might not look credible, and you may lose the opportunity to convert prospects.

The easiest way to emphasize your brand and appear legitimate is to use your logo!

It’s a simple yet effective way to help recipients instantly identify and recognize your brand.

If you want to do something a bit more comprehensive, you could also insert your business tagline.

Branding is essential to getting recipients to read through your emails, but it isn’t the ONLY thing that captures readers’ attention. Check out my guide on how to start an email to captivate email recipients with stunning openers.

2. A/B Test Your Pre-Header Text

Consistency is key to driving brand performance, right?

However, that doesn’t mean your pre-header text has to remain the same for every email.

Consider A/B testing your emails with different pre-header text.

This involves sending variations of emails with slightly different pre-header text to different parts of your email list. You can then monitor how each batch did (in terms of engagement, opens, etc.) to decide which pre-header text to use.

3. Use Fonts That Are “Web-Safe”

If you were printing a physical newsletter, you’d have full control over how the end product looks.

However, emails aren’t necessarily like that.

Whatever content you include in an email is encoded before being sent to the recipient and then decoded when it reaches their inbox.

If you use fancy or rare fonts, they may not show up on your recipient’s device. This means your email won’t look the way you intended it to look — which could impact how well it engages the reader.

Always stick to classic, “web-safe” fonts that are sure to show up on any device. This way, you can control how your email message will look on most recipients’ devices.

Arial, Courier, Georgia, Tahoma, Times New Roman, Trebuchet MS, and Verdana are a few examples of web-safe fonts.

4. Make Your Pre-Headers Personalized

The personalized pre-header text is essential to drive up marketing performance.

Think about it.

Would you rather read an email with generic pre-header text or something that addresses you personally?

But how do you personalize dozens or hundreds of outgoing marketing emails at once?

Just use GMass!

It’s an email outreach tool that works entirely within Gmail, and all you need to do is download the GMass Chrome extension to get started.

How does GMass help you personalize your emails?

GMass has an automatic email personalization feature. It can automatically identify a recipient’s first name from their email address and insert it into an email addressed to them. You can even include personalized company names, industry names, and images!

GMass also has a new feature that allows you to send conditional content on email campaigns.

You can use these features to instantly personalize the pre-header text of hundreds or even thousands of bulk marketing emails.

What is An Email Header - How To Design Great Pre-Header Text

Wrapping Up

Email headers play a crucial role in ensuring that your emails have the data they need to be delivered successfully. They’re also key in helping you determine the origin and legitimacy of your emails.

However, don’t forget how important your pre-header text is — especially when it comes to increasing email marketing engagement. Just follow the tips I’ve mentioned in this article to see how simple adjustments to your email pre-header text can boost your conversion rates.

And if you’re looking for the perfect email marketing tool to send out your marketing emails, look no further than GMass. Sign up today to give your email campaigns an instant boost!

4 Comments
  1. The spam checker for my email said there should be an unsubscribe link in the header. You don’t mention that here – how, why, when should I put an unsubscribe link in the header? thanks (happy gmass customer, btw)

    1. Hi David,

      Unfortunately, at this time, GMass doesn’t have the feature to add an unsubscribe link in your email header. Though we can’t guarantee it, it may be something we can add in our roadmap ahead.

  2. Why isn’t there a way to view an email header when using Hotmail or Gmail on an Android phone? The options just aren’t there.

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