An email header is an important section of the message that contains detailed technical information about the route and origin of the message. This information is useful for diagnosing delivery issues, identifying the sender’s mail server, detecting possible spoofing attempts, and much more.
Header information
Once you can view the header, you will see information such as:
- From: The sender’s email address.
- To: The recipient’s email address.
- Date: The date and time the email was sent.
- Subject: The subject of the message.
- Received: Information about the servers the email passed through on its way to your inbox.
In addition, it may contain other specific fields related to authentication, content type, etc.
To view the header of an email, the steps vary depending on the email client you are using. Below we show how to do it in some of the most common email clients:
Gmail
- Open the email you want to analyze.
- Click on the three vertical dots in the upper-right corner of the message.
- Select “Show original” from the drop-down menu. This will open a new tab with the email’s source code, including the header.
Outlook (web version)
- Open the email you want to check.
- Click the down arrow next to “Reply” at the top of the message.
- Select “View source” from the drop-down menu. This will display the message’s source code, which includes the header.
Thunderbird (email client)
- Open the email you want to check.
- Click “View” in the menu bar.
- Select “Headers” and then “All” to view the full email header.
Mail on Mac (macOS)
- Open the email you want to view.
- In the menu bar, select “View” and then “Message”.
- Then choose “All Headers” to display the full message header.
SOGo / cdmon Webmail
- Open the email you want to view.
- In the email, click the arrow located in the upper-right corner (below the three horizontal lines).
- A section will expand showing all the header information.