The email header is a code snippet in the HTML email document, which contains information about the sender, the recipient, the email’s route to get to the inbox, and various authentification details. Email header always precedes the email body.

What purpose do email headers serve?

  • Provide information about the sender and recipient. An email header tells who sent the email and where it arrived. There are markers which indicate this information, like “From:” which stands for sender’s name and email address, “To:” — recipient’s name and email address, and “Date:” — time and date when the email was sent. All of these are mandatory indicators. Other parts of email header are optional and differ among email service providers.
  • Prevent from spamming. The information displayed in the email header helps email service providers to troubleshoot potential spam issues. ESP analyzes the email header, the “Received:” tag, in particular, to decide whether to deliver an email or not.
  • Identify the email route. When an email is sent from one computer to another, it transfers through the Mail Transfer Agent which automatically “stamps” the email with information about the recipient, time and date in the email header. 

How to find an email header?

All ESPs enable curious users to see how the email looks from the inside, as an HTML code. This function looks and works the same in every ESP. Let’s have a closer look at it.

How to view an email header in Gmail?

Open an email. Find “More” (three vertical dots), choose “Show original.”

Email header in Gmail

How to view an email header in Outlook?

Open an email. Find “More actions” (three horizontal dots), choose “View message source.”

Email header in Outlook

How to view an email header in Yahoo?

Open an email. Find “More actions” (three horizontal dots), choose “View raw message.”

Email header in Yahoo

How to analyze an email header?

The appearance of the email header differs among email service providers. To analyze it, you need to find the email header and examine the lines which interest you. All the code from the beginning until the tag <body> represents the header. Here is the list of what you can find in the email header:

  • “Received:” lines. They show the address of the computer which receives the email, as well as other computers’ addresses which an email could have been transferred through. Unlike other email header’s elements, “Received:” lines can’t be forged.Received lines
  • MIME-version. Multipurpose Internet Mail Extensions is an Internet standard that extends the format of email for supporting text and non-text attachments like audio, video, images, etc., message bodies with multiple parts, etc.MIME-version
  • Message ID. Message-ID is a globally unique identifier used in email. Message-IDs have a specific format which is a subset of an email address and there are no two different messages that bear the same Message-ID.Message ID
  • DKIM Signatures. DomainKeys Identified Mail confirms the sender’s authenticity by connecting the domain name with the email. DKIM is the technology that helps to reduce spam and phishing and allows companies to vouch for their email messages.DKIM signatures

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