How to interpret email headers
What are email headers?
Email headers are the information that accompanies an email message, such as the sender, the recipient, the date, the subject, and other details. Email headers are not usually visible to the average user, but they can be accessed by using certain tools or commands. Email headers are useful for troubleshooting, tracking, and verifying email messages.
How do email headers work?
Email headers are composed of several fields, each with a name and a value, separated by a colon. For example, a typical email header might look like this:
From: Alice <alice@example.com>
To: Bob <bob@example.com>
Subject: Hello
Date: Tue, 15 Jun 2021 10:00:00 +0000
Message-ID: <1234567890@example.com>
Each field has a specific meaning and function. Some of the most common fields are:
- From: The email address of the sender.
- To: The email address of the recipient.
- Subject: The brief summary of the message.
- Date: The date and time when the message was sent.
- Message-ID: A unique identifier for the message, usually generated by the sender's email server.
There are also many other fields that can be added by the sender, the recipient, or the intermediate servers that handle the email delivery. Some of these fields are:
- CC: The email addresses of the carbon copy recipients, who receive a copy of the message.
- BCC: The email addresses of the blind carbon copy recipients, who receive a copy of the message without being visible to other recipients.
- Reply-To: The email address where replies to the message should be sent.
- Received: The information about the servers that processed the message along the way, such as their names, IP addresses, and timestamps.
- Content-Type: The format and encoding of the message body, such as plain text, HTML, or multipart.
- MIME-Version: The version of the Multipurpose Internet Mail Extensions (MIME) standard that the message conforms to.
- X-: The prefix for any custom or non-standard fields that are added by the sender or the servers, such as X-Spam-Status, X-Originating-IP, or X-Mailer.
Why are email headers important?
Email headers are important for several reasons, such as:
- They provide essential information about the origin, destination, and content of the message.
- They help to identify and prevent spam, phishing, and spoofing, by allowing the recipient to verify the authenticity and integrity of the message.
- They help to troubleshoot and resolve any issues or errors that may occur during the email delivery, by allowing the sender and the recipient to trace the path and the status of the message.
- They help to analyze and improve the performance and security of the email system, by allowing the administrators and the users to monitor and optimize the email traffic and the email behavior.
What are the limitations of email headers?
Email headers are not without limitations, such as:
- They can be forged or manipulated by malicious actors, who can alter or add fields to deceive the recipient or the servers.
- They can be incomplete or inaccurate, due to human errors, technical glitches, or intentional omissions by the sender or the servers.
- They can be complex and confusing, due to the variety and the inconsistency of the fields and the formats that are used by different email systems and standards.
- They can be inaccessible or unreadable, due to the lack of tools or skills by the average user, or the encryption or compression of the message or the headers.
How to understand email headers?
To understand email headers, one needs to:
- Know how to access the email headers, by using the appropriate tools or commands for the email client or the webmail service that is used to send or receive the message.
- Know how to read the email headers, by recognizing the names and the values of the fields, and understanding their meanings and functions.
- Know how to interpret the email headers, by analyzing the information and the evidence that they provide, and verifying their validity and reliability.
There are also many online tools and resources that can help to understand email headers, such as:
- Email header analyzers, that can parse and display the email headers in a user-friendly way, and highlight any anomalies or issues that may be present.
- Email header validators, that can check and confirm the authenticity and the integrity of the email headers, and detect any signs of forgery or manipulation.
How to view email headers
To view the email headers of an email message, you can use the following steps depending on your email client or web browser:
- In Gmail, open the email message and click on the three dots icon next to the reply button. Then, select "Show original" from the menu.
- In Outlook, open the email message and click on the "File" tab. Then, select "Properties" from the menu.
- In Thunderbird, open the email message and click on the "View" menu. Then, select "Message Source" from the menu.
- In Chrome, open the email message and right-click on the page. Then, select "View page source" from the menu.
- In Firefox, open the email message and right-click on the page. Then, select "View page source" from the menu.
- In Safari, open the email message and click on the "Develop" menu. Then, select "Show page source" from the menu.
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