Summary
Identifying a company's spam filter involves a multifaceted approach, combining technical analysis, testing, and understanding of major email security providers. Analyzing rejection messages, SMTP logs, and MX records helps reveal filtering mechanisms. Tools like MXToolbox, GlockApps, Litmus, Snov.io, Mailjet, SendPulse, and Gmass aid in testing deliverability, checking blacklists, monitoring IP reputation, and setting up seed lists. Analyzing SPF, DKIM, and DMARC records offers insights into authentication practices. Resources like Spamhaus blocklists provide valuable data. Documentation from Microsoft (EOP), Google Workspace, Cisco (ESA), Barracuda, and Proofpoint explain their respective filtering techniques. When facing blocks, examining error messages and URLs from blocklist operators is crucial. Seed lists offer insights but require diverse seeds from multiple providers. Lastly, recognizing the complexity of Outlook's delivery is vital.
Key findings
- Rejection Analysis: Analyzing rejection messages and SMTP logs helps uncover spam filtering details.
- Infrastructure Checks: Checking MX records and IP ownership identifies mail servers and potential filtering services.
- MXToolbox: MXToolbox helps identify mail servers and filtering services through domain name analysis.
- Authentication Records: Analyzing SPF, DKIM, and DMARC records reveals authentication practices and potential spam filters.
- Spamhaus Blocklists: Spamhaus maintains blocklists to identify spam sources.
- Deliverability Testing: GlockApps and Litmus test email deliverability and identify spam filter triggers.
- Blacklist Checks: Snov.io offers tools for blacklist checks to identify potential spam filtering issues.
- IP Reputation: Mailjet monitors IP reputation, revealing potential spam filter triggers.
- Seed Lists: Gmass suggests seed list testing to identify providers filtering emails as spam.
- Email Testing Tools: SendPulse offers email testing tools to check deliverability and identify spam triggers.
- Major Provider Techniques: Microsoft EOP, Google Workspace, Cisco ESA, Barracuda, and Proofpoint documentation reveals their filtering techniques.
- Blocklist Information: Examining error messages and URLs from blocklist operators provides details when blocked.
Key considerations
- Combine Methods: Employ a combination of methods for a comprehensive understanding of spam filtering practices.
- Error Message Specificity: Error messages vary in detail, necessitating careful analysis.
- Statistical Significance: Interpret seed list results cautiously due to limited statistical significance.
- Provider Relationships: Seed provider relationships with mailbox providers influence seed weighting.
- Outlook Complexity: Delivering to Outlook presents unique challenges due to its intricate filtering mechanisms.
- Admin Access: Administrative access is often needed to view spam filter reports and settings.
- Tool Expertise: Select testing and analysis tools that align with your technical expertise.
- Dynamic Filters: Spam filters evolve continuously, requiring ongoing monitoring and testing.
What email marketers say
9 marketer opinions
Identifying a company's spam filter involves several techniques. MXToolbox helps by revealing mail servers and filtering services through domain name analysis. Analyzing SPF, DKIM, and DMARC records provides insights into authentication practices. Bounce messages (NDRs) contain details about filtering mechanisms. Tools like GlockApps and Litmus test deliverability and identify spam filter triggers. Blacklist checks via Snov.io and IP reputation monitoring with Mailjet can reveal potential issues. Seed list testing, as suggested by Gmass, shows which providers filter emails as spam. Finally, SendPulse offers email testing to identify deliverability and spam triggers.
Key opinions
- MXToolbox: MXToolbox can identify mail servers and filtering services by analyzing domain names.
- Authentication Records: Analyzing SPF, DKIM, and DMARC records can reveal email authentication practices and potential spam filters.
- Bounce Messages: Bounce messages (NDRs) provide information about spam filtering mechanisms.
- Deliverability Testing: GlockApps and Litmus test email deliverability and identify spam filter triggers.
- Blacklist Checks: Snov.io offers tools for blacklist checks to identify potential spam filtering issues.
- IP Reputation: Mailjet monitors IP reputation, revealing potential spam filter triggers.
- Seed Lists: Gmass suggests seed list testing to identify providers filtering emails as spam.
- Email Testing Tools: SendPulse offers email testing tools to check deliverability and identify spam triggers.
Key considerations
- Multiple Techniques: A combination of techniques provides the most comprehensive understanding of a company's spam filtering practices.
- Tool Variety: Various tools exist for testing and analysis; select the ones that best fit your needs and technical expertise.
- Dynamic Filters: Spam filters are constantly evolving, so regular monitoring and testing are essential.
- False Positives: Deliverability testing may trigger false positives; interpret results cautiously.
Marketer view
Email marketer from EmailToolTester explains that GlockApps can be used to test email deliverability and identify spam filters. It sends emails to various mailboxes and provides reports on placement in inbox, spam folder, or missing status.
27 Aug 2021 - EmailToolTester
Marketer view
Email marketer from Gmass shares that setting up seed list testing involves sending test emails to a variety of email addresses across different providers. The results can indicate which providers are filtering your emails as spam.
2 Sep 2023 - Gmass
What the experts say
4 expert opinions
Identifying a company's spam filter involves several investigative steps. Examining rejection messages and their SMTP logs, as well as MX records and IP ownership, can reveal the filters in use. When blocked, check error messages and associated URLs for details from blocklist operators. Seed lists are useful for delivery monitoring, but their results lack statistical significance and should include diverse seeds from multiple providers. Dealing with Outlook's delivery can be particularly challenging due to its complex and often opaque filtering mechanisms.
Key opinions
- Rejection Analysis: Google rejection messages and analyze SMTP logs to find clues about the spam filter being used.
- Infrastructure Checks: Check MX records and IP ownership to identify the mail servers and potential filtering services.
- Blocklist Information: If blocked, review error messages and URLs provided by blocklist operators for details.
- Seed List Limitations: Seed lists are helpful but limited; ensure diversity in seed selection and consider multiple providers.
- Outlook Complexity: Outlook's delivery is complex and often inexplicable, posing unique challenges.
Key considerations
- Combine Methods: Use a combination of methods to gain a comprehensive understanding of a company's spam filtering practices.
- Error Message Specificity: Error messages vary in detail; some may require additional investigation.
- Statistical Significance: Seed list results should be interpreted cautiously due to limited statistical significance.
- Provider Relationships: Different seed providers have varying relationships with mailbox providers, affecting seed weighting.
- Outlook Nuances: Delivering to Outlook may require specific strategies due to its unique challenges.
Expert view
Expert from Email Geeks shares that when you get rejections you can google the messages. They’re often distinctive. They also shares they tend to lookup the MX; it’s often obvious from there. If not, check the IP ownership of the MX servers.
7 Nov 2021 - Email Geeks
Expert view
Expert from Word to the Wise explains that seed lists can be a helpful part of your delivery monitoring, but they aren't the only thing to use. Seed list results are not statistically significant (you usually have very few seeds per domain). You want a variety of seeds, including different geographies and business types. Different seed providers weight seeds differently based on their relationship with mailbox providers. There are benefits to using different providers.
1 Mar 2023 - Word to the Wise
What the documentation says
6 technical articles
Identifying a company's spam filter involves understanding the filtering techniques used by major email security providers. Exchange Online Protection (EOP) utilizes connection filtering, spam signature filtering, and heuristic analysis, with admin reports available. Spamhaus maintains blocklists identifying spam sources. Gmail employs machine learning and provides admin reports. Cisco ESA uses reputation, content, and outbreak filters. Barracuda Spam Firewall uses real-time intent analysis, Bayesian filtering, and sender reputation. Proofpoint Email Protection uses a multi-layered approach with reputation, content, and threat analysis. Each system provides admins with customization and reporting options.
Key findings
- EOP Techniques: Exchange Online Protection (EOP) employs connection, signature, and heuristic filtering.
- Spamhaus Blocklists: Spamhaus maintains blocklists to identify spam sources.
- Gmail ML: Gmail uses machine learning algorithms for spam filtering.
- Cisco ESA: Cisco ESA uses reputation, content, and outbreak filters.
- Barracuda Methods: Barracuda uses real-time intent, Bayesian, and sender reputation analysis.
- Proofpoint Layers: Proofpoint uses reputation, content, and threat analysis in a multi-layered approach.
Key considerations
- Admin Access: Administrative access is often required to view spam filter reports and settings.
- Diverse Techniques: Spam filters use a variety of techniques, including reputation, content, and connection analysis.
- Machine Learning: Modern email systems increasingly rely on machine learning for spam detection.
- Customization: Administrators can often customize filtering policies based on organizational needs.
- Regular Reporting: Regular review of spam filter reports is essential for maintaining email security.
Technical article
Documentation from Spamhaus explains that Spamhaus maintains various blocklists (e.g., SBL, XBL, PBL) that identify IP addresses and domains known for sending spam. Checking whether a company's mail server IP is listed on these blocklists can indicate the use of Spamhaus filtering.
12 Feb 2025 - Spamhaus
Technical article
Documentation from Cisco explains that the Cisco Email Security Appliance (ESA) uses various techniques such as reputation filtering, content analysis, and outbreak filters to identify and block spam. Admins can configure and monitor spam filtering policies through the ESA interface.
7 Jul 2021 - Cisco
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