How to Use an SMTP Header Analyzer for Email Forensics and Trace Email Origins

How to Use an SMTP Header Analyzer for Email Forensics and Trace Email Origins

In today’s world, email remains a central means of communication. While email provides convenience and instant connectivity, it can also be exploited for malicious purposes. Email forensics—the process of analyzing emails to detect fraudulent or harmful activity—is an essential skill in digital security. One of the most powerful tools in email forensics is the SMTP header analyzer. It allows investigators to trace the origins of an email, determine its path through various mail servers, and even identify potential sources of malicious activity. SMTP Header Analyzer

In this article, we’ll explore how to use an SMTP header analyzer to trace the origins of an email, detect potential threats, and gather forensic data to support investigations. Whether you're a cybersecurity professional, a legal expert, or simply someone curious about email tracing, understanding SMTP headers and how to analyze them is a crucial skill.

What Is an SMTP Header?

The SMTP header is a block of metadata attached to every email message that includes vital routing information. SMTP, which stands for Simple Mail Transfer Protocol, is the protocol used by mail servers to send and receive emails across the internet.

An SMTP header includes information such as:

• Sender's information: The email address, name, and the server from which the email was sent.


• Recipient’s information: The email address and server to which the message was delivered.


• Message routing: Details about the servers that handled the email’s transmission from the sender to the recipient.


• Timestamps: Information about when the email was sent, processed, and received.


• IP addresses: The originating IP address of the email sender and intermediate servers.


• Authentication information: Whether the email passed security checks such as SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), or DMARC (Domain-based Message Authentication, Reporting, and Conformance).

SMTP headers can provide a detailed map of how an email traveled across the internet, making them an invaluable resource for email forensics.

Why Use an SMTP Header Analyzer?

An SMTP header analyzer is a tool designed to decode and analyze the raw SMTP headers of an email. By examining these headers, you can extract crucial information to understand the email’s origin, the route it took, and whether any malicious activity was involved. Some common use cases for an SMTP header analyzer include:

• Tracing email origins: Identifying the originating server of an email, which can help trace the sender’s physical location or detect if an email was spoofed.


• Investigating phishing or spam emails: Tracking down the source of malicious emails that might be trying to steal personal information or distribute malware.


• Detecting email spoofing: Identifying if an email has been altered to make it appear as if it was sent from a legitimate source.


• Forensics in legal cases: Collecting evidence for legal investigations, particularly in cases involving harassment, fraud, or identity theft.

By analyzing SMTP headers, you can often identify hidden details that aren't visible in the email’s content, providing a deeper layer of insight into the email's legitimacy.

Steps for Using an SMTP Header Analyzer

To get started with email forensics, you'll first need to extract the SMTP header from an email. Here’s a step-by-step guide on how to do this and use an SMTP header analyzer effectively.

Step 1: Extract the SMTP Header

Before you can analyze an email’s SMTP header, you need to extract it. This process varies depending on the email client or service you're using. Here’s how to do it in some of the most popular platforms:

• Gmail:
  
  
  
  1. Open the email in Gmail.
  
  
  2. Click on the three dots in the upper-right corner of the email.
  
  
  3. Select Show Original.
  
  
  4. A new window will open with the raw email content, including the SMTP header. Copy this entire block of text.
  
  
  
  


• Outlook:
  
  
  
  1. Open the email in Outlook.
  
  
  2. Click on the File tab.
  
  
  3. Select Properties.
  
  
  4. In the Properties window, you’ll see the Internet headers section. Copy the contents of this section.
  
  
  
  


• Yahoo Mail:
  
  
  
  1. Open the email in Yahoo Mail.
  
  
  2. Click on the More Options button (three dots) in the upper-right corner.
  
  
  3. Select View Raw Message.
  
  
  4. Copy the SMTP header from the new window.
  
  
  
  

Step 2: Choose an SMTP Header Analyzer

Once you’ve copied the email’s SMTP header, the next step is to paste it into an SMTP header analyzer. Several online tools allow you to do this, with some of the most reliable options being:

• MXToolbox (https://mxtoolbox.com/EmailHeaders.aspx)


• WhatIsMyIP.com’s Email Header Analyzer (https://www.whatismyip.com/email-header-analysis/)


• Message Header Analyzer by Microsoft (https://testconnectivity.microsoft.com/)


• IPVoid (https://www.ipvoid.com/email-header-analyzer/)

These tools will decode the raw header, break it down into its components, and provide a detailed report on the email’s routing.

Step 3: Analyze the SMTP Header Report

After pasting the header into the analyzer, you’ll receive a breakdown of the information contained in the SMTP header. Key elements to pay attention to include:

1. Received Fields:
   
   
   
   • The Received lines in the header show the path an email took from sender to recipient, including the mail servers it passed through. The first Received line will show the sender’s mail server, and each subsequent line shows the intermediate servers the email passed through before reaching its destination.
   
   
   • Look for the IP address associated with each server in this chain. This can help you determine the geographic location of the sender, or identify any suspicious or unexpected servers that might indicate malicious activity.
   
   
   
   


2. Return Path:
   
   
   
   • The Return-Path field contains the address to which bounce-back messages are sent. This is often the first place to check when investigating email spoofing.
   
   
   
   


3. Authentication Results:
   
   
   
   • SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) are authentication methods used to verify whether an email was sent from a trusted source. Look for fields like "spf=pass" or "dkim=pass" to confirm the email’s legitimacy. If these are marked as “fail” or “neutral,” the email may be suspicious.
   
   
   
   


4. Sender’s IP Address:
   
   
   
   • The sender’s IP address is crucial for tracing the email back to its origin. Using an IP lookup tool, you can often determine the location of the sender and even the specific organization or ISP associated with the address.
   
   
   
   


5. Message ID:
   
   
   
   • The Message-ID is a unique identifier for the email message. It can be useful in tracking specific emails and tracing their origins across different systems.
   
   
   
   


6. Date and Time:
   
   
   
   • Timestamps provide insight into when the email was sent and when it was processed by various servers. By checking the timestamps, you can verify if the email’s delivery timeline matches the expected path.
   
   
   
   

Step 4: Interpret the Results

Once you have the results from the analyzer, you can interpret them to trace the email’s origin. Key things to look for include:

• Suspicious IP Addresses: If the email originates from an unexpected or unknown location, it could be a red flag indicating phishing or other malicious activity.


• Inconsistent Routing: A large number of “Received” lines or servers that don’t match the sender’s usual routing path may indicate the email was routed through unusual servers, which is common in spoofed or fraudulent emails.


• Authentication Failures: If an email fails authentication checks like SPF or DKIM, it may be an indication that the email has been tampered with or is from a malicious source.

Step 5: Take Action Based on the Analysis

Once you’ve thoroughly analyzed the SMTP header and gathered relevant information, take the appropriate action based on your findings. This could involve:

• Reporting a phishing email to the relevant authorities or email provider.


• Blocking or blacklisting suspicious IP addresses.


• Investigating further into the email’s sender or domain.

Conclusion

Using an SMTP header analyzer for email forensics is a powerful way to trace the origin of an email, verify its authenticity, and detect potential threats like phishing, spam, and email spoofing. By extracting and analyzing the SMTP header, you can gain valuable insights into how an email was routed, the servers involved, and whether the email passed security checks. In an increasingly digital world, mastering email forensics is an essential skill for protecting yourself and your organization from malicious actors.