How can I identify the ESP used to send a spam email using the email headers?

Summary

Identifying the ESP (Email Service Provider) used to send a spam email involves a multi-faceted approach centered on email header analysis. Key techniques include examining 'Received:' headers to trace the email's path, performing reverse IP lookups on server IPs found in headers, and analyzing 'Authentication-Results,' SPF, and DKIM records. Understanding which entity controls the infrastructure and looking for specific ESP identifiers are also important. Tools like MXToolbox's Email Header Analyzer and specialized services offered by experts can further assist in the identification process. The analysis of SMTP extensions and the Return-Path header provides supplementary information. Overall, a comprehensive understanding of email header structure and ESP-specific practices is crucial for accurate identification.

Key findings

  • Received Headers Trace: 'Received:' headers are fundamental for tracing an email's origin and identifying the involved servers.
  • Reverse IP Lookup: Performing reverse IP lookups on IPs from 'Received:' headers helps identify the hostname and potentially the ESP.
  • Authentication Analysis: Analyzing 'Authentication-Results,' SPF, and DKIM records reveals authentication details and the sending source.
  • Return-Path Analysis: The 'Return-Path' header indicates the bounce-handling domain, which can point to the ESP.
  • ESP Identifiers: Specific identifiers or server names associated with known ESPs can be found within headers.
  • Infrastructure Control: Identifying the entity controlling the sending infrastructure is crucial.
  • Analysis Tools: Header analysis tools (e.g., MXToolbox) automate parsing and interpretation of email headers.
  • Expert Assistance: Experts offer tools and services for identifying ESPs from email headers.
  • SMTP Extensions: Examining SMTP extensions sometimes provides indications of the ESP.

Key considerations

  • Technical Expertise: Email header analysis requires technical knowledge and understanding of email protocols.
  • Header Forging: Spammers can forge headers, complicating ESP identification.
  • Tool Accuracy: Ensure the accuracy and reliability of header analysis tools.
  • Configuration Variation: ESPs have varying configurations, which affects header analysis.
  • Combined Techniques: Employing a combination of analysis techniques yields the most accurate results.

What email marketers say
8Marketer opinions

Identifying the ESP (Email Service Provider) used to send a spam email through email headers involves several techniques. Key methods include performing reverse IP lookups on the sending server's IP address found in the 'Received:' headers, examining SPF and DKIM records, analyzing the 'Return-Path' header, looking for specific ESP identifiers in the headers, using header analysis tools, correlating IP addresses with known ESP ranges, and checking the 'Authentication-Results' header. These methods combined offer a comprehensive approach to pinpointing the ESP behind a spam email.

Key opinions

  • Reverse IP Lookup: Performing a reverse IP lookup on the sending server's IP (from 'Received:' headers) can reveal the associated organization or ESP.
  • SPF & DKIM Records: Examining SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) records helps identify authorized sending sources and potentially the ESP.
  • Return-Path Analysis: Analyzing the 'Return-Path' header often reveals the domain used by the ESP for bounce handling, aiding in ESP identification.
  • ESP Identifiers: Looking for specific identifiers or server names associated with well-known ESPs within the header information can be effective.
  • Header Analysis Tools: Using header analysis tools can automatically parse and interpret email headers, simplifying ESP identification.
  • IP Correlation: Correlating IP addresses in 'Received:' headers with known IP ranges used by various ESPs helps identify the sender.
  • Authentication-Results Header: Examining the 'Authentication-Results' header provides information about DKIM and SPF checks, which can indicate the ESP.

Key considerations

  • Multiple Methods: Using a combination of methods provides a more comprehensive and accurate identification of the ESP.
  • Header Interpretation: Accurate interpretation of email headers is crucial, requiring an understanding of header structure and ESP-specific patterns.
  • Tool Reliability: The reliability and accuracy of header analysis tools should be considered when selecting and using them.
  • Evolving Techniques: Spammers may use techniques to obfuscate headers, requiring ongoing adaptation of identification methods.
Marketer view

Email marketer from EmailDeliverabilityPro shares to correlate the IP addresses found in the 'Received:' headers with known IP ranges used by various ESPs to identify the sender.

April 2024 - EmailDeliverabilityPro.com
Marketer view

Email marketer from Reddit explains that you can perform a reverse IP lookup on the sending server's IP address (found in the 'Received:' headers) to identify the organization or ESP associated with that IP.

January 2022 - Reddit
Marketer view

Email marketer from EmailBlackListCheck explains to examine the 'Authentication-Results' header, if present, as it often contains information about the DKIM and SPF checks, which can indicate the ESP.

November 2021 - EmailBlackListCheck.net
Marketer view

Email marketer from StackExchange explains that examining the SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) records in the email headers can help identify the authorized sending sources and potentially reveal the ESP.

September 2021 - StackExchange
Marketer view

Email marketer from EmailDripGuru shares to look for specific identifiers or server names commonly associated with well-known ESPs within the header information.

January 2025 - EmailDripGuru.com
Marketer view

Email marketer from EmailSecurityFAQ explains that analyzing the Return-Path header often reveals the domain used by the ESP for bounce handling, which can help identify the ESP.

June 2023 - EmailSecurityFAQ.com
Marketer view

Email marketer from Mailhardener shares to use header analysis tools to identify ESP or brand names embedded within the headers. This includes examining DKIM signatures, SPF records, and other custom header fields that often contain identifying information.

February 2022 - Mailhardener.com
Marketer view

Email marketer from EmailGeekForum explains that using online header analyzer tools to automatically parse and interpret email headers can make identifying the ESP easier, as these tools highlight relevant information and relationships.

July 2024 - EmailGeekForum.com

What the experts say
6Expert opinions

Identifying the ESP used to send a spam email involves analyzing email headers for key indicators. Experts recommend focusing on 'Received:' headers to trace the email's path via IP addresses and hostnames, performing reverse DNS lookups on identified IP addresses to determine the hostname and potentially the ESP. Examination of the 'Authentication-Results' header for DKIM and SPF details is also crucial. Understanding which entity controls the infrastructure is important too. Additionally, some experts offer tools and services to help with this identification process.

Key opinions

  • Received Headers: 'Received:' headers are crucial for tracing an email's origin using IP addresses and hostnames of involved servers.
  • Reverse DNS Lookup: Performing a reverse DNS lookup on identified IP addresses can reveal the hostname and potentially the ESP.
  • Authentication Results: 'Authentication-Results' header provides DKIM, SPF, and other authentication details, potentially revealing the ESP.
  • Infrastructure Control: Understanding which entity controls the underlying infrastructure is critical for identifying the ESP.
  • Expert Tools: Some experts offer specialized tools and services to help identify ESPs from email headers.

Key considerations

  • Header Complexity: Analyzing email headers can be complex and require technical expertise.
  • Header Forging: Spammers might forge headers, making identification more difficult.
  • Varying Configurations: ESPs have different configurations and authentication practices, impacting header analysis.
  • Tool Reliability: The accuracy and reliability of ESP identification tools can vary.
Expert view

Expert from Word to the Wise explains the 'Authentication-Results' header provides details on the DKIM, SPF, and other authentication checks performed on the email, potentially revealing the sending ESP if they are properly configured.

February 2023 - Word to the Wise
Expert view

Expert from Spam Resource explains that the 'Received:' headers are key to tracing an email's origin, as they contain the IP addresses and hostnames of the servers that processed the email. By examining these, you can often identify the ESP used.

August 2022 - Spam Resource
Expert view

Expert from Email Geeks offers to help identify the ESP from email headers if a sample is provided.

March 2025 - Email Geeks
Expert view

Expert from Word to the Wise shares that when analyzing email headers, understanding which entity controls the underlying infrastructure that sent the email (servers, IP addresses) is critical to identifying the ESP.

January 2023 - Word to the Wise
Expert view

Expert from Spam Resource shares that once you've identified an IP address from the 'Received:' headers, perform a reverse DNS lookup to determine the hostname. This hostname often contains the name of the ESP or sending organization.

April 2021 - Spam Resource
Expert view

Expert from Email Geeks shares that they have a tool to identify the ESP based on the IP address and offers to check samples or IPs.

October 2021 - Email Geeks

What the documentation says
5Technical articles

Identifying the ESP (Email Service Provider) of a spam email through email headers involves examining 'Received:' lines in the full headers to trace the email's path through servers. Microsoft Outlook allows viewing internet headers under 'File,' then 'Properties'. Tools like MXToolbox's Email Header Analyzer can parse headers to identify sending servers. RFC documents explain the structure of 'Received:' headers, aiding in identifying ESPs. Examining SMTP extensions, as detailed by IANA, can sometimes reveal the ESP.

Key findings

  • Received Headers: 'Received:' lines within full email headers trace the email's path through various servers.
  • Outlook Header Access: Microsoft Outlook allows accessing internet headers under 'File' -> 'Properties'.
  • MXToolbox Analyzer: MXToolbox's Email Header Analyzer can parse email headers to identify sending mail servers.
  • RFC Structure: RFC documents detail the structure and meaning of 'Received:' headers for accurate analysis.
  • SMTP Extensions: Examining SMTP extensions, according to IANA, can sometimes indicate the ESP.

Key considerations

  • Header Complexity: Analyzing email headers requires technical knowledge to interpret the information correctly.
  • Header Manipulation: Spammers might manipulate headers, making accurate identification difficult.
  • Tool Dependence: Relying solely on automated tools might not always provide a complete or accurate picture.
  • Regular Updates: Keep up-to-date with the latest email header formats and analysis techniques.
Technical article

Documentation from RFC Editor explains the structure and meaning of 'Received:' headers, which contain valuable information about the path an email takes, including server addresses and timestamps, and can assist in pinpointing the originating ESP.

April 2024 - RFC-Editor.org
Technical article

Documentation from IANA explains that examining SMTP extensions used during the email sending process (often visible in the headers) can sometimes indicate the ESP, as different ESPs might use specific extensions.

March 2021 - IANA.org
Technical article

Documentation from Microsoft Support shares that in Outlook, you can view internet headers by opening the email, clicking 'File,' then 'Properties,' and looking under the 'Internet headers' section to analyze the routing information.

June 2023 - Microsoft Support
Technical article

Documentation from MXToolbox explains that you can use MXToolbox's Email Header Analyzer to paste the full email headers and identify the sending mail servers, which may help determine the ESP.

May 2023 - MXToolbox
Technical article

Documentation from Google Workspace Admin Help explains that you can trace an email's origin by examining the full email headers, particularly the 'Received:' lines, which show the path the email took through various servers.

August 2024 - Google Workspace Admin Help