What is an Email Header?

An email header is a snippet of code attached to the beginning of an email message which contains key details about the email’s sender, recipient, date and time of sending, and routing information. The code is typically hidden from the recipient’s view but can be accessed if necessary.




What Does an Email Header Contain?

An email header contains several components which provide key information to the email server. These components include the following fields: 

  • From:

    The sender’s email address. This field usually contains the sender’s display name as well. This field can be spoofed in phishing attacks, so verifying the sender’s identity through additional methods is important.

  • To:

    The email recipient’s address. When there are multiple recipients, they are all included in this field, separated by commas.

  • Subject:

    The email title, as displayed in the subject line.

  • Message-ID:

    A unique identifier assigned to each email message. It helps to track and reference the email, especially in threaded conversations and replies.

  • Received:

    This shows the email’s path from the sender to the recipient. This is useful for diagnosing delivery issues and identifying the origin of spam emails.

  • Return-Path

    The return-path specifies the email address to which bounce messages (undeliverable notifications) should be sent.

  • Reply-To:

    This is the email address to which replies should be sent. Occasionally, this differs from the “From” email address.

  • Content-Type:

    This specifies the format of the email’s content. I.e., whether it contains just plain text, HTML, or attachments.

  • MIME-Version:

    This field indicates the version of the Multipurpose Internet Mail Extensions (MIME) protocol used in the email.

  • Date:

    The date and time the email was sent. It follows a specific format (RFC 5322) and helps organize emails chronologically.


What Are Email Headers Used For?

Email headers are essential for facilitating safe and reliable email communication, They ensure proper delivery and provide critical information for email management and security. With an email header, you can:


Trace an Email


Email headers provide a detailed route of the email’s journey, which is essential for tracing the origin of suspicious or malicious emails. This information helps identify sources of spam and phishing attacks.


Troubleshoot Delivery Issues


Headers can reveal problems in the email delivery process, such as delays or failures. Administrators can diagnose and resolve delivery issues by examining the “Received” fields and timestamps.


Filter Spam Emails


Email headers contain clues that help spam filters determine an email’s legitimacy. Filters analyze headers for signs of spoofing, unusual routing, and other indicators of spam or phishing attempts.


Ensure Email Compliance & Security


Headers ensure compliance with email standards and security protocols. They include information about authentication mechanisms like SPF, DKIM, and DMARC, which help verify the sender’s identity and protect against spoofing




How to View an Email Header

The email header code snippet is hidden by default on most email clients. Should you want to manually read the header, you can:



Click on “show original” in the dropdown menu on the top-right corner




Click the “File tab” on the message window, then click “Info” in the left column, and finally click on “Properties”



How to Read an Email Header

There are two ways to read an email header:


1. Manually:

Once you open the email header file, you can manually read the contents. Use the search function to find the field that you’re looking for


2. Using an email header analyzer:

Alternatively, you can use an email header analyzer to read the contents. Popular options include MX ToolBox and DNS Checker

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