Summary
Effectively blocking disposable email domains (DEDs) and problematic top-level domains (TLDs) is essential for maintaining email list hygiene and improving deliverability. The most robust approach involves implementing real-time email validation APIs at the point of data entry, which dynamically check against comprehensive, updated lists of known DEDs. In addition to these APIs, leveraging widely available open-source GitHub lists of DEDs provides a flexible and cost-effective method for developers to integrate blocking mechanisms directly into their systems. For managing problematic TLDs, especially for inbound email, administrators can configure email gateway solutions or server-level rules to block or quarantine emails from high-risk domains, as some TLDs are consistently associated with spam or low-quality engagement. Consistent monitoring of bounce rates and integrating tools like reCAPTCHA further enhance defense against new DEDs and bot-driven sign-ups, while overall list hygiene practices remain paramount for long-term email marketing success.
Key findings
- APIs are Most Effective: Real-time email validation APIs that maintain comprehensive, updated lists of known DEDs are cited as the most effective method to block disposable email domains, preventing instant sign-ups or submissions from temporary addresses.
- GitHub Lists are Widely Used: Many developers and marketers rely on frequently updated open-source lists of disposable email domains available on GitHub for integration into registration forms, offering a cost-effective solution.
- Specific TLDs are Problematic: Certain TLDs, such as '*.ml', are consistently identified as problematic, rarely yielding legitimate subscribers or leads, and are often associated with spam or malicious activities.
- Gateway Solutions for TLD Blocking: Advanced email security platforms and gateway solutions like Barracuda Networks and Proofpoint utilize threat intelligence to identify and block emails originating from malicious TLDs, preventing spam and phishing attempts.
- Prevention is Key: Blocking disposable email domains and problematic addresses at the point of entry is crucial for improving overall deliverability and reducing bounce rates, rather than managing them post-acquisition.
Key considerations
- Point of Entry Validation: Integrating email validation APIs at the point of data entry, such as sign-up forms, is the most effective proactive strategy to prevent disposable email domains (DEDs) and other problematic addresses from ever reaching your list. This helps maintain list hygiene, improves deliverability, and reduces bounce rates.
- Leverage Open-Source Lists: Regularly updated open-source lists of disposable email domains, often found on GitHub, provide a valuable resource for developers to integrate into their backend systems, allowing for programmatic blocking without constant API calls. These lists require consistent updating to remain effective.
- Implement TLD Filtering: For inbound email, administrators can configure email gateway solutions or server settings, like Postfix, to block or quarantine emails from specific problematic top-level domains (TLDs) known for spam or phishing. While direct TLD blocking isn't common for outbound marketing, inbound systems frequently use TLD reputation.
- Combine Methods: For robust protection, combine email validation APIs with tools like reCAPTCHA to deter bots that often use DEDs. Additionally, consistently monitoring bounce rates can help identify new or emerging problematic domains not yet on blocklists.
- Continuous List Hygiene: Beyond blocking at entry, consistent email list hygiene, including the removal of addresses associated with problematic TLDs and inactive accounts, is fundamental for long-term deliverability and avoiding spam traps. Email verification services can assist in identifying various problematic address types.
What email marketers say
10 marketer opinions
Safeguarding email deliverability and maintaining a clean subscriber base necessitates robust strategies for identifying and blocking disposable email domains and high-risk top-level domains. Implementing real-time email validation services at the point of subscriber acquisition is paramount, as these tools actively prevent problematic addresses from entering your list. Marketers and developers frequently leverage widely available open-source lists of disposable email domains, often found on platforms like GitHub, which can be integrated into registration systems. Additionally, while direct TLD blocking is less common for outbound marketing, inbound email systems and anti-spam filters often assign reputation scores to TLDs. A comprehensive approach includes continuous list hygiene, diligent monitoring of bounce rates, and employing technologies such as reCAPTCHA to deter bot-driven sign-ups that frequently utilize DEDs, ensuring only legitimate subscribers are on your list.
Key opinions
- API-based Validation is Key: Integrating email validation APIs at the point of entry is the most effective strategy for proactively blocking disposable email domains, which significantly improves deliverability and reduces bounce rates.
- Open-Source Lists are Valuable: Many developers rely on regularly updated open-source lists of disposable email domains, often found on platforms like GitHub, for integration into registration forms.
- Certain TLDs Are Problematic: Specific TLDs, such as *.ml, are frequently cited as problematic due to a consistent lack of legitimate subscribers and high association with spam.
- Inbound Systems Use TLD Reputation: While direct TLD blocking is uncommon for outbound email, inbound email systems and anti-spam filters often assign reputation scores to TLDs.
- Prevention at Entry is Crucial: Preventing problematic email addresses from ever reaching your list through validation at the point of data entry is fundamental for maintaining list hygiene and overall deliverability.
Key considerations
- Prioritize Point-of-Entry Validation: Implement email validation APIs or services at all data capture points to proactively block disposable email domains and prevent problematic addresses from entering your email list.
- Leverage Open-Source Blacklists: Utilize and integrate regularly updated open-source lists of disposable email domains, available on platforms like GitHub, into your registration and signup processes.
- Monitor and Avoid Problematic TLDs: Be aware that certain top-level domains may be consistently associated with low-quality or spammy engagements; ensure your subscriber acquisition processes focus on reputable sources.
- Regularly Analyze Bounce Rates: Continuously monitor your email campaign bounce rates, as an increase can signal new or emerging disposable domains that need to be addressed.
- Combine Tools for Robust Protection: Supplement email validation services with other protective measures, such as reCAPTCHA to deter bots and ongoing list hygiene practices to maintain a clean and engaged subscriber base.
- Explore Platform-Specific Solutions: For popular content management systems like WordPress, investigate and utilize plugins designed to automatically block disposable email domains or check against known spam TLDs.
Marketer view
Marketer from Email Geeks suggests using the ivolo/disposable-email-domains GitHub list as a master list for blocking and recommends checking Spamhaus and Symantec's lists of shady top-level domains (TLDs) for filtering purposes.
7 Feb 2024 - Email Geeks
Marketer view
Marketer from Email Geeks shares that the *.ml TLD is often problematic and has not yielded legitimate subscribers or leads.
1 Jan 2022 - Email Geeks
What the experts say
2 expert opinions
This content focuses on utilizing specialized email validation services, particularly real-time validation during the signup process, as the primary defense against disposable email domains and other low-quality addresses. This proactive approach is highlighted as more effective than relying on static blacklists due to the constantly evolving nature of temporary email addresses. Combining such validation services with other protective measures like CAPTCHAs and behavioral monitoring is recommended to ensure robust list hygiene, prevent problematic sign-ups, and ultimately improve email deliverability and engagement.
Key opinions
- Validation Services are Core: Professional email validation services are fundamental for maintaining list hygiene by identifying and removing disposable email accounts, spam traps, and inactive mailboxes, thus improving overall email health.
- Real-Time Signup Prevention: Implementing real-time validation at the point of user signup is crucial for preventing problematic email addresses from ever reaching your list, leading to better deliverability and engagement.
- Blacklisting Limitations: Relying solely on static blacklists for disposable email domains is not advised due to their dynamic nature and the inherent risk of generating false positives, which can block legitimate subscribers.
- Multi-layered Approach: A comprehensive strategy involves combining real-time validation services with additional preventative measures like CAPTCHAs and behavioral monitoring for more robust protection against low-quality sign-ups.
Key considerations
- Prioritize Dynamic Validation: Focus on utilizing email validation services that offer dynamic, real-time checks at the moment of subscription rather than depending on static domain blacklists, which can quickly become outdated.
- Comprehensive Validation Scope: Choose services that not only identify disposable domains but also check for valid syntax, active mailboxes, and potential spam traps to ensure robust list quality and improved deliverability.
- Integrate Early in the Funnel: Deploy validation processes directly into your sign-up forms and data capture points to block low-quality or temporary email addresses before they ever contaminate your email list.
- Augment with Anti-Bot Measures: Enhance your validation efforts by integrating tools like CAPTCHAs and behavioral monitoring to deter automated bot sign-ups that frequently use disposable email addresses, providing a multi-layered defense.
- Focus on Engagement: By preventing problematic addresses from entering your list, these strategies directly contribute to higher engagement rates and significantly improved email deliverability over time.
Expert view
Expert from Spam Resource explains that email validation services are a key strategy for maintaining list hygiene by identifying and removing problematic addresses, including disposable email accounts, spam traps, and inactive mailboxes. These services check for valid syntax, active mailboxes, and can help prevent sign-ups from low-quality or temporary email addresses, thereby improving deliverability and engagement.
27 Feb 2025 - Spam Resource
Expert view
Expert from Word to the Wise explains that a key strategy for protecting email lists from disposable email addresses (DEAs) is to implement real-time validation at the point of signup. She advises against solely relying on blacklisting specific DEA domains due to their dynamic nature and the potential for false positives. Instead, services that can identify DEAs during the subscription process, coupled with measures like CAPTCHAs and behavioral monitoring, are recommended to prevent low-quality sign-ups and maintain list hygiene, thereby improving deliverability.
23 Feb 2023 - Word to the Wise
What the documentation says
7 technical articles
To maintain robust email deliverability and list quality, a multi-faceted strategy for blocking disposable email domains (DEDs) and problematic top-level domains (TLDs) is essential. This involves leveraging both real-time validation services at subscriber entry points and integrating self-managed, updated lists of known DEDs into backend systems. For managing inbound email, security platforms and server configurations offer capabilities to filter or block emails from high-risk TLDs, preventing spam and phishing. These proactive measures are critical for ensuring list hygiene and overall campaign effectiveness, minimizing bounces and protecting recipient inboxes.
Key findings
- Real-Time APIs are Highly Effective for DEDs: Documentation highlights that real-time email validation APIs with comprehensive, updated lists are the most effective method for instantly blocking disposable email domains at the point of submission.
- Self-Managed DED Lists are Viable: Developers can integrate publicly available or GitHub-hosted lists of disposable email domains into their backend systems, offering a programmatic, cost-effective blocking solution that requires regular updates.
- Email Gateways Filter Problematic TLDs: Solutions from SpamTitan, Proofpoint, and Barracuda Networks allow administrators to implement content filtering rules to block or quarantine inbound emails from problematic TLDs often associated with spam or phishing.
- Server Configurations Enable TLD Blocking: Email server configurations, such as Postfix, can be modified using sender restrictions and regular expression maps to block emails originating from specific undesirable top-level domains.
- Threat Intelligence Enhances TLD Blocking: Advanced email security platforms utilize threat intelligence to identify and proactively block emails from malicious TLDs, preventing spam and phishing attempts.
Key considerations
- Prioritize Real-Time API Validation: For blocking disposable email domains (DEDs), integrating a real-time email validation API at signup or submission points is highly effective, as these services maintain dynamically updated lists of known DEDs.
- Utilize and Update Open-Source DED Lists: Developers can integrate publicly available or GitHub-hosted lists of disposable email domains directly into their applications, providing a cost-effective solution, though consistent updates are crucial for effectiveness.
- Implement Gateway and Server-Level TLD Filtering: For inbound email, administrators should configure email gateway solutions or server settings, such as Postfix, to block or quarantine emails originating from specific problematic top-level domains (TLDs) known for spam or phishing.
- Leverage Threat Intelligence in Security Platforms: Advanced email security platforms offer capabilities to identify and block emails from newly registered or historically malicious TLDs using sophisticated threat intelligence.
- Combine Approaches for Comprehensive Protection: For robust defense, combine real-time API validation for DEDs with direct integration of open-source DED lists, alongside robust TLD filtering at the email gateway or server level.
Technical article
Documentation from ZeroBounce Docs explains that the most effective way to block disposable email domains is to use a real-time email validation API that maintains and updates a comprehensive list of known DEDs. This allows businesses to prevent sign-ups or submissions from temporary addresses instantly.
17 Nov 2022 - ZeroBounce Docs
Technical article
Documentation from SpamTitan explains that administrators can implement content filtering rules within their email gateway solutions to block inbound emails originating from specific problematic top-level domains (TLDs) or to quarantine them for review, especially those frequently associated with spam or phishing.
19 Nov 2023 - SpamTitan Docs
How can I filter and sanitize a large list of email domains using DNS and other techniques?
How can I fix spam trap issues related to disposable email domains and low open rates?
Should I block disposable email addresses from my email list?
What are the best lists of temporary email account generators and should they be blocked?
What open 'bad domain' lists can I use to filter newsletter subscriptions from typo domains?
Where can I find comprehensive lists of known disposable email domains to block?
