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What is an email header?

Email marketing is the business of building relationships. However, there are numerous challenges that email marketers can face in their attempt to do this, so it’s helpful for every marketer to have an understanding of the technical aspects of email communication.

There are many features of email that get little attention, but that serve a crucial function in improving the overall experience. The email header is an example of such a feature.

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What is an email header? What do email headers do? What information is included in an email header? Conclusion

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What is an email header?

An email header is a data snippet in an email. Email headers contain critical metadata that is used to deliver and authenticate email messages. Due to all of the important information they can contain, email headers are regarded as valuable informational resources for marketers.

An email header typically precedes the message body text of the email itself, though custom headers must be accessed elsewhere depending on the client in use.

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What do email headers do?

Email headers contain data about who sends and receives a message, as well as the subject, date of sending, and much more. These pieces of information are mandatory elements and are part of all email headers.

However, email headers also play a role in the prevention of malicious attacks. Email service providers can use headers to help them distinguish between spammers and legitimate senders. What’s more, they can use the routing information in headers to trace the path of an email, determine the source IP address, and identify attackers.

From a marketer’s perspective, headers can be a useful tool for testing before a send-out. By addressing emails to oneself and viewing the headers, it’s possible to avoid potential issues with deliverability in email marketing campaigns.

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What information is included in an email header?

Because there are many elements of an email’s metadata that are optional to include, there is a high level of variance between email headers. However, the following are the most commonly used header tags that are useful to know:

  • From: This tag includes details about the sender of the email.
  • To: This field provides information about email recipients, including their name and email address.
  • Date: This field contains a timestamp indicating when the email was initially sent.
  • Subject: This field contains the information found in the subject line of the email.
  • Return Path: This indicates where servers should send bounced emails. This is also known as the bounce address.
  • MIME version: This header denotes that the email in question complies with the rules of MIME (Multipurpose Internet Mail Extensions), an SMTP protocol that allows users to send images, audio, video, and application files via email.
  • Envelope-To: This header indicates that the message was delivered to a specified email address.
  • Received: This header provides information on the servers through which a message has passed.
  • Reply-to: This field provides a specified email address to which recipients can send their replies.
  • Message-ID: This field contains a sequence of numbers and letters that identify the message in question. Each message ID is completely unique.
  • Content-type: This header indicates the type of media content contained in the message, such as text, HTML, or jpeg.
  • DKIM signature and DomainKeys: This tag contains DomainKeys and DKIM signatures used to authenticate emails against the sender domain.
  • X-Spam-Status: This field indicates whether or not an email message is regarded as spam and provides a numerical score.
  • X-Spam-Level: This header is contingent on the numerical score provided in the X-Spam-Status header. Each point gained is represented by an asterisk (*) here.

Conclusion

Email headers are a feature of email communication that is often overlooked. However, they play an important role in fostering transparency in online communication. 

An email header provides a useful source of information when trying to avoid phishing attacks, troubleshoot issues, and indicate the source of delivery issues.

Header information provides insights into the journey that an email takes. For an email marketing professional, those insights could prove invaluable. All told, becoming acquainted with email headers and how to use them could very well be the difference maker when it comes to achieving success with your email campaigns.

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