What are email headers and how to forward an email including it’s headers?

Every email message consists of 3 different parts:

1. The envelope. Invisible to the user, seen only by mail servers with instructions how, where, to whom and when to deliver the message
2. The headers. Partly visible (the ‘subject’, ‘To’ and ‘From’ header data are always visible), but mostly invisible to the user. It includes a lot of information about how the mail was routed, which mail servers were involved in transportation and what has been done with the message (verificaton checks, etc.) by which mail server.
3. The body. Fully visible with the content of the message.

If you want or need to inspect the hidden header data you need to take special steps to make it visible. For example, if you receive a fraudulent email, it can be very useful to see the header data and to send a full forensic copy to the email provider, an organization that is being spoofed, industry partners, or even law enforcement.

Usually, when a user clicks forward in a mail client, the client copies the message’s content and attachments to a new message. The original message headers are not included when forwarding a message as usual.

Email headers contain very useful information for tracing a message’s origin and troubleshooting its delivery. Email headers are written with the oldest headers at the bottom, and the newest headers at the top. By reading the headers in the correct order, you can see how the message was passed from one mail server to another, and the actions each mail server took along the way.

Most email clients have a function to display a message’s headers. The exact steps depends on the client. The steps on some clients are described below.

Apple Mail on macOS

How to see the header

• Select the message or open it
• In the Menu Bar, click ‘View’ > ‘Message’ > ‘All Headers’

How to forward the header

• Right click on the message in the list of messages
• Click Forward as Attachment
• Fill in the ‘To’ field and send it

Apple Mail on iOS (iPhone or iPad)

It is not possible to see message headers at those mail clients.

E-Mail on Android Smartphones

It is not possible to see message headers at those mail clients.

SOGo Webmail (Mailix Business Webmail option)

How to see the header

• Open the message
• Click on the three vertical dots in the upper right
• Click on ‘View Message Source’
• The complete source, including all headers cam be seen

How to forward the header

• Open the message
• Click on the three vertical dots in the upper right
• Click on ‘Download Message’ and save the file to your device.
• Start a new email message and attach the downloaded .eml file

Roundcube Webmail (Mailix Family Webmail option)

How to see the header

• Open the message
• Click on the three horizontal dots in the upper right labeled ‘More’
• Click on ‘Show Source’
• The complete source, including all headers cam be seen in a new window

How to forward the header

• Open the message
• Click on the three horizontal dots in the upper right labeled ‘More’
• Click on ‘Download’ > ‘Source (.eml)’ and save the file to your device
• Start a new email message and attach the downloaded .eml file

Windows 10 Mail app

How to see the header

• Open the message
• Click on the three horizontal dots in the upper right
• Click Save As, and save the email as a file
• Open the file in a text editor

How to forward the header

• Open the message
• Click on the three horizontal dots in the upper right
• Click ‘Save As’, and save the email as a file
• Attach the saved file to a new email and send it

Gmail/G Suite webmail

How to see the header

• Open the message
• Click on the three vertical dots in the upper right
• Click ‘Show original’
  The message headers are located at the top part of the message source, under the ‘Copy to clipboard’ button.

How to forward the header

• Open the message
• Click on the three vertical dots in the upper right
• Click Show original
• Click Download Original, save it, and send it as an attachment in a new message

Outlook.com/Office 365 webmail

How to see the header

• Open the message
• Click on the three horizontal dots in the upper right
• Scroll down in the menu, and click ‘show message details’

How to forward the header

• Open the web mail in two browser windows
• Create a new email in one browser window
• In the other browser window, drag the email you want to attach from your email list, and drop it in the blank email
• Fill out the ‘To’ field, and send it

Outlook for macOS

How to see the header

• Right click on the message in the list of messages
• Click ‘View Source’
  The message headers are located at the top of the message source.

How to forward the header

• In the messages list, right click the message you want to forward
• Click ‘Forward As Attachment’
• Fill in the ‘To’ field, and send it

Outlook for Windows

How to see the header

• Open the message
• Click File
• Under the ‘Info’ category click on the ‘Properties’ button.
  The headers are listed as “Internet headers”

How to forward the header

• Create a new email
• Drag the message you want to forward from the messages list and drop it in the blank message body
• Fill in the ‘To’ field, and send it

Thunderbird

How to see the header

• Open the message
• Click on the three vertical dots in the upper right
• Click ‘view message source’

How to forward the header

• In the messages list, right click on the message you want to forward (or select multiple messages and then right click)
• Select ‘Forward as attachment’
• Fill in the ‘To’ field and send it