Email. It's the backbone of modern communication. But behind the friendly facade lies a complex network of servers, protocols, and hidden data. Understanding email headers is crucial for diagnosing delivery issues, identifying spam, and verifying the sender's authenticity. This is where an email header analyzer comes in handy.
This article will explore what an email header analyzer does, how it works, and why it's an essential tool for anyone dealing with email communication. We'll also delve into the intricacies of various header fields, authentication methods, and trace routes.
An email header analyzer is a tool designed to dissect and interpret the raw data found in an email's header. The tool, such as the one offered by WintelGuy.com, presents this information in a readable format, highlighting key details about the email's journey from sender to recipient.
What information can you get from email headers?
An email header analyzer parses the text of the header section. This section, separate from the email body, contains fields that adhere to a specific syntax defined in standards like RFC5322. The WintelGuy.com Email Header Analyzer then extracts and presents the information in a user-friendly format. It’s important to note that these tools rely solely on header data and DNS information and do not actively detect forged headers.
An email header is divided into fields, each containing a field name and a field body, separated by a colon. These fields provide a wealth of information about the email's origin and path.
Key Header Fields:
"From:", "Sender:", "Reply-To:" - Indicate the email's author and how to respond."Date:" - The date and time the email was sent."To:", "Cc:", "Bcc:" - Specify the recipients of the email."Subject:", "Message-ID:", "In-Reply-To:", "References:" - Help identify and thread email conversations."Return-Path:", "Received:" - Show the route the email took.Every email server that handles an email adds a "Received:" field to the header. These fields, grouped together with the most recent one at the top, trace the email's journey.
Example "Received:" Field:
Received: from mail-vs1-f52.google.com (mail-vs1-f52.google.com [209.85.217.52]) by mail81130c14.megamailservers.com (mail81130c14) with ESMTPSA id D1214925EACB1; Sun, 25 Jul 2021 12:28:43 -0400 (EDT)
This field reveals:
"from mail-vs1-f52.google.com (mail-vs1-f52.google.com [209.85.217.52])""by mail81130c14.megamailservers.com (mail81130c14)""with ESMTPSA id D1214925EACB1""Sun, 25 Jul 2021 12:28:43 -0400 (EDT)"More information about the "Received:" fields including the sections of the field can be found in RFC5321, Section 4.4.
Several header fields are dedicated to email authentication, helping to combat spam and phishing.
Authentication-Results: Shows the outcome of authentication checks like SPF, DKIM, and DMARC (RFC8601).
Example:
Authentication-Results: mx.example.com; spf=pass smtp.mailfrom=example.com; dkim=pass header.d=example.com; dmarc=pass header.from=example.com
Received-SPF: Indicates the result of the Sender Policy Framework (SPF) check (RFC7208). Example:
Received-SPF: pass (example.com: domain of sender@example.com designates 192.0.2.1 as permitted sender)
DKIM-Signature: Contains the DomainKeys Identified Mail (DKIM) signature, verifying the message's integrity (RFC6376).
Example:
DKIM-Signature: v=1; a=rsa-sha256; d=example.com; s=selector1; c=relaxed/relaxed; q=dns/txt; h=from:to:subject:date; bh=abc123...; b=def456...
For more details on the DKIM-Signature, you can refer to the IANA - DomainKeys Identified Mail (DKIM) Parameters registry.
Authenticated Received Chain (ARC) Headers: ARC-Seal, ARC-Message-Signature, and ARC-Authentication-Results work together to validate intermediary mail systems during transit, preserving authentication results (RFC8617). Example:
ARC-Seal: i=1; a=rsa-sha256; d=example.com; s=selector1; t=1625247603; cv=none; b=abc123...
ARC-Message-Signature: i=1; a=rsa-sha256; d=example.com; s=selector1; t=1625247603; h=from:to:subject:date; bh=def456...; b=ghi789...
ARC-Authentication-Results: i=1; mx.example.com; spf=pass smtp.mailfrom=example.com; dkim=pass header.d=example.com; dmarc=pass header.from=example.com
Non-standard header fields, often starting with "X-", can provide additional, custom information. For example, "X-Mailer:" might indicate the email client used, while "X-Origin-Country:" could suggest the sender's geographic location.
Email header analysis is a vital skill for system administrators, security professionals, and anyone who wants a deeper understanding of how email works. Tools like WintelGuy.com's Email Header Analyzer simplify the process, providing valuable insights into the hidden world of email headers. By understanding these headers, you can gain greater control over your email communication and protect yourself from potential threats. You can find resources and more information by viewing the WintelGuy.com resources page.
Use Wintelguy's SPF record lookup and other e-mail tools for a comprehensive view.
