Summary
Email validation services play a crucial role in maintaining list hygiene and improving deliverability, especially when integrated into registration pages. While these third-party products offer valuable benefits by filtering out invalid, disposable, or high-risk email addresses, they are not without their limitations and margins of error. Effective strategies often involve a combination of using these tools, understanding their nuances, and implementing internal policies to manage flagged addresses.
Key findings
- Tool adoption: Many companies utilize third-party services like TheChecker and Kickbox for real-time validation on registration forms.
- Accuracy variance: There are noticeable differences in accuracy and detection rates (e.g., spam traps, honeypots) among validation providers, with higher-priced services often offering more robust checks.
- Cost vs. quality: Some users find certain popular services, such as ZeroBounce, to be disproportionately expensive relative to their perceived accuracy or the number of flagged issues.
- Proactive vs. reactive: It is generally advised to use email validation services during contact acquisition rather than solely for post-hoc list cleaning, as bounces will already be handled by your ESP.
Key considerations
- Handling flagged addresses: Businesses must decide how to treat email addresses identified as undeliverable, disposable, or low-quality. Options include immediate rejection, soft rejection with a retry prompt, or accepting but immediately unsubscribing them.
- Spam trap detection: Claims by validation services about detecting spam traps and honeypots should be critically evaluated, as verifying such claims is often difficult due to proprietary data.
- Disposable and role-based emails: Consider policies for disposable email addresses and + tagging. While some companies ban + addresses due to trial cycling, others view them as a sign of legitimate user behavior. Learn more about preventing disposable email signups.
- Engagement focus: Beyond initial validation, prioritizing subscribers based on actual email activity and engagement is becoming a more important factor for deliverability. This aligns with broader best practices for improving email deliverability. OneSignal provides additional insights on how to verify and validate email addresses before sending.
What email marketers say
Email marketers frequently discuss the practical application of third-party validation services on registration pages, often sharing their experiences with specific vendors and the resulting impact on their email lists. Their perspectives highlight both the benefits and frustrations associated with these tools, especially regarding accuracy, pricing, and how different services handle various types of problematic email addresses.
Key opinions
- Positive experiences: Some marketers report high accuracy with tools like TheChecker, especially for filtering out undeliverable and disposable emails.
- Concerns about specific vendors: There are strong criticisms regarding the accuracy of certain services, such as Email Oversight, which have been observed to miss a significant percentage of spam traps.
- B2B vs. B2C suitability: Kickbox is often praised for its effectiveness with B2B data, suggesting that some tools perform better with specific data types.
- Pricing perceptions: The pricing of services like ZeroBounce is considered high by some, leading them to seek more cost-effective alternatives.
Key considerations
- Score-based acceptance: Marketers frequently implement policies to accept only email addresses above a certain validation score provided by the service (e.g., Kickbox's 0-100 score). This helps to prevent low-quality sign-ups. More information on preventing suspicious contacts.
- Post-purchase handling: For purchase forms, some marketers accept all emails but immediately pass low-scoring addresses to an unsubscribe list, allowing users to opt back in if desired. This is a strategy to prevent fake registrations.
- Handling plus-addressing: Marketers may decide to disallow + addresses (e.g., email+tag@gmail.com) to prevent trial cycling, although this can sometimes alienate legitimate users who use this feature for tracking or filtering. Skrapp.io provides further insights into choosing an email verifier tool.
- Suppressing disposable domains: Utilizing lists of known disposable domains from validation services to suppress these addresses from all sends is a common practice.
Marketer view
A marketer from Email Geeks states that their company uses TheChecker and finds its accuracy to be very high, particularly for filtering out undeliverable and disposable email addresses. They accept all emails except those explicitly flagged as such, helping to maintain a clean list from the point of entry.
Marketer view
A marketer from Email Geeks believes that ZeroBounce, despite its popularity, has an unreasonably high price point compared to the value it provides. This has led them to explore alternative email validation solutions that offer better cost-efficiency without compromising too much on accuracy.
What the experts say
Industry experts provide a more critical and technical perspective on third-party email validation, often questioning the claims of providers and emphasizing the complexities involved in accurate email hygiene. Their insights frequently touch upon the underlying data sources, the limitations of current technologies, and the evolving landscape of deliverability where engagement plays an increasingly vital role.
Key opinions
- Skepticism on spam trap claims: Many experts are skeptical about providers' claims of knowing honeypots and spam traps, particularly those asserting partnerships with major blocklist operators without verifiable proof. You can learn more about how spam traps work.
- Data accuracy disparity: Testing multiple services reveals significant disparities in scan results and accuracy, despite sales promises of robust detection methods. This underscores the need for thorough vetting of services to find the best email address validation tools.
- Shifting validation focus: There's a growing trend to move beyond static email validation towards dynamic email activity and engagement data to prioritize subscribers, recognizing engagement as a key deliverability factor.
- Risks of certain providers: Some services are identified as potentially problematic, with concerns that some data hygiene providers may even be associated with snowshoe or botnet activities.
Key considerations
- Proprietary data claims: Claims of exclusive relationships with 'largest purveyors of honeypots' are difficult to confirm, highlighting the opaque nature of some validation service methodologies. Email Tool Tester has a good comparison of email marketing services.
- Limitations of validation for existing lists: For existing lists, most bounces are already accounted for. Validation services primarily help with new contact acquisition, though they can identify catch-all mailboxes as potential risks.
- Role of data sharing: Services like Fresh Address may collect hashed delivery logs and SMTP response codes from ESPs to improve their validation accuracy. The breadth of such data partnerships likely contributes to their effectiveness.
- Treatment of plus-addressing: While + addressing can be used for trial cycling, experts often view it as a legitimate signal that a company is collecting emails organically rather than through questionable means. Prohibiting them can deter legitimate users.
Expert view
An expert from Email Geeks warns that all email validation providers are likely overstating their ability to identify honeypots and spam traps, especially those that claim unverifiable partnerships with major blocklist entities. This suggests a need for caution when evaluating such services.
Expert view
An expert from Email Geeks observes that Webbula claims an exclusive relationship with the world's largest purveyor of honeypots, a claim that is impossible to confirm independently. This highlights a common issue of transparency within the email validation industry regarding data sources.
What the documentation says
The foundational principles of email validation are rooted in technical standards and best practices established by internet protocols. Documentation from various sources, including RFCs (Request for Comments) and industry guidelines, outlines the expected behavior of email systems and the criteria for determining a valid and deliverable email address. These guidelines form the basis for how third-party validation tools operate, yet real-world implementation often involves complex considerations beyond mere technical compliance.
Key findings
- Syntax validation: Email validation begins with checking the email address against RFC standards for proper formatting (e.g., presence of @ symbol, valid characters, domain structure).
- Domain existence: Checking for a valid domain by verifying MX (Mail Exchange) records is a critical step to ensure the domain can receive emails.
- Disposable email detection: Many validation services maintain extensive lists of known disposable or temporary email domains to help filter out low-quality sign-ups.
- SMTP connection tests: Performing real-time SMTP handshake tests can identify if an email address actually exists on a server without sending an email. This includes detecting 'catch-all' addresses or temporary errors.
Key considerations
- Grey areas: Even with comprehensive checks, some valid email addresses might be flagged due to server-side configurations (e.g., aggressive spam filters, greylisting) or temporary issues, necessitating careful handling of 'unknown' or 'risky' statuses. You can learn more about understanding greylisting.
- Privacy compliance: Using third-party services requires adherence to data privacy regulations (e.g., GDPR, CCPA) as email addresses are personal data. This includes ensuring the validation provider has appropriate security measures and data processing agreements. Termly provides resources on privacy policies for email marketing.
- Trade-offs: Relying on validation tools can reduce bounce rates and spam trap hits, but over-filtering can lead to legitimate sign-ups being rejected. A balance must be struck based on the business's risk tolerance and acquisition goals. This is part of the broader strategy for preventing bad signups.
- Dynamic factors: Email validity is not static. Accounts can become inactive, domains can change, or new spam trap techniques can emerge. Continuous monitoring and periodic re-validation are necessary, even with initial checks at registration.
Technical article
RFC 5322, the specification for internet message format, defines the syntax rules for email addresses. Documentation clarifies that while these rules are strict, many email validation tools go beyond basic syntax to include deliverability checks, which are not directly covered by RFCs but are crucial for actual email sending.
Technical article
Email deliverability best practices documentation emphasizes the importance of validating email addresses in real-time at the point of collection. This proactive approach significantly reduces bounce rates and minimizes the risk of accumulating invalid or harmful addresses on mailing lists, protecting sender reputation.
Related resources
11 resources
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