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
8 marketer 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.
1 Jul 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.
20 Apr 2025 - Reddit
What the experts say
6 expert 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.
3 Jan 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.
12 Nov 2023 - Spam Resource
What the documentation says
5 technical 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.
21 Jun 2022 - 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.
10 Dec 2024 - IANA.org
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