What are the best list validation services and when should I use them?

Summary

The consensus is that list validation and regular cleaning are crucial for email deliverability, protecting sender reputation, and improving engagement. While some experts recommend specific services like Kickbox, ZeroBounce, and Hunter.io, others emphasize focusing on permission-based marketing and data collection. List validation identifies and removes invalid, risky, and low-quality email addresses through techniques like syntax checks and mailbox pings. A cautious approach is advised, recognizing potential inaccuracies and integrating validation within a comprehensive list hygiene strategy.

Key findings

  • Benefits of Validation: List validation improves deliverability, sender reputation, ROI, and engagement by removing bad addresses.
  • Validation Methods: Email validation uses syntax checks, domain checks, and mailbox pings to identify invalid addresses.
  • Frequency of Cleaning: Lists should be cleaned regularly and before each email campaign.
  • Services Mentioned: Kickbox, ZeroBounce, Hunter.io, Email Oversight, and Validity are mentioned as validation service options.
  • Transparency is Key: Some validation services may lack transparency regarding the company's leadership and permission practices.
  • Accuracy Considerations: List validation may not always be accurate; be aware of false positives and supplement it with other strategies.
  • Alternative Strategy: Proper permission practices and data collection are more effective long-term compared to relying on validation.

Key considerations

  • Holistic Approach: Integrate list validation into a comprehensive strategy that includes permission-based practices and data collection.
  • False Positives: Be aware that some valid email addresses may be incorrectly identified as invalid.
  • Regular Maintenance: Maintain a schedule for regular list cleaning to ensure optimal deliverability and engagement.
  • Transparency: Research the validation provider to verify its business and data practices.
  • Balance with Data Quality: Ensure you are using other methods alongside validation to collect high quality email address data.

What email marketers say
9Marketer opinions

Experts and marketers recommend using list validation services to remove invalid, risky, and low-quality email addresses from email lists. This practice helps prevent deliverability issues, protect sender reputation, reduce bounce rates, and increase engagement rates. Several services are mentioned, including Kickbox, Email Oversight, Validity, ZeroBounce, and Hunter.io. However, it's also advised to be wary of false positives and to use list validation in conjunction with other list hygiene practices.

Key opinions

  • Benefits: List validation improves deliverability, protects sender reputation, reduces bounce rates, and increases engagement.
  • When to Use: List validation should be used regularly to maintain a healthy email list and before sending email campaigns.
  • Services: Recommended services include Kickbox, Email Oversight, Validity, ZeroBounce, and Hunter.io.
  • Accuracy: List validation services may not always be accurate, and false positives can occur.

Key considerations

  • Holistic Approach: Use list validation as part of a broader list hygiene strategy, not as a standalone solution.
  • False Positives: Be aware that list validation services might incorrectly identify valid email addresses as invalid.
  • Regular Maintenance: Cleaning email lists should be done on a regular basis to maintain optimal deliverability and engagement.
Marketer view

Email marketer from NeverBounce.com states that list validation should be used to identify and remove invalid, risky, and low-quality email addresses from your marketing list. They say this leads to improved deliverability and higher engagement rates.

February 2025 - NeverBounce.com
Marketer view

Email marketer from Medium shares to use email verification before sending emails. Verifying email addresses helps reduce bounce rate by deleting bad or invalid email addresses, which in turn protect sender reputation.

January 2025 - Medium.com
Marketer view

Email marketer from Litmus recommends regularly cleaning your email list to remove invalid and inactive email addresses to improve deliverability and engagement rates.

August 2023 - Litmus.com
Marketer view

Marketer from Email Geeks recommends researching Kickbox, Email Oversight, and Validity (formerly Bright Verify) when looking for validation companies.

July 2021 - Email Geeks
Marketer view

Email marketer from Emailhippo.com shares that email verification helps prevent deliverability issues, protects sender reputation, and improves overall email marketing performance by removing invalid and risky email addresses.

July 2022 - Emailhippo.com
Marketer view

Email marketer from ZeroBounce.net explains that list validation services should be used to remove invalid and harmful email addresses, reducing bounce rates and improving sender reputation. They also share that they should be used regularly to maintain a healthy email list.

June 2023 - ZeroBounce.net
Marketer view

Email marketer from Quora recommends using ZeroBounce or Hunter.io as email verification services to ensure email deliverability and avoid blacklisting.

February 2022 - Quora
Marketer view

Email marketer from Reddit explains that in their opinion list validation services can be useful but are not always accurate and to be wary of false positives, so should be used in conjunction with other list hygiene practices.

March 2025 - Reddit
Marketer view

Email marketer from StackExchange shares that cleaning an email list helps improve sender reputation, reduce bounce rates, and increase engagement rates.

August 2023 - StackExchange

What the experts say
3Expert opinions

Experts have varying opinions on list validation. One expert expresses concern about the lack of transparency surrounding Clearout.io, suggesting caution. Another expert generally doesn't recommend email validation but suggests Kickbox for clients who insist. A third expert advises focusing on permission practices, data collection, and subscriber engagement as a more effective approach than relying solely on validation tools.

Key opinions

  • Transparency Concerns: Lack of transparency in a validation service provider can be a red flag.
  • Alternative Focus: Prioritizing permission practices and subscriber engagement may be more effective than solely relying on validation tools.
  • Conditional Recommendation: If validation is deemed necessary, Kickbox is mentioned as a potential option.

Key considerations

  • Company Transparency: Research the validation service provider and ensure transparency in their operations and leadership.
  • Permission-Based Marketing: Focus on building a permission-based email list through proper data collection and subscriber engagement strategies.
  • When to Validate: Consider whether email validation is truly necessary, and if so, use it as part of a broader strategy that includes permission and engagement.
Expert view

Expert from Word to the Wise advises focusing on permission practices and deliverability instead of relying solely on validation tools. They suggest focusing on good data collection and subscriber engagement as a more effective approach to managing email lists.

May 2022 - Word to the Wise
Expert view

Expert from Email Geeks shares concerns about Clearout.io, noting the lack of transparent information about the company's founders and leadership. She is suspicious of companies that do not disclose who is behind them, and the LinkedIn connections appear to be from “less than permission based marketers”. She finds it weird that every link clicked on websites associated with them redirects through clearout.io

October 2021 - Email Geeks
Expert view

Expert from Email Geeks states that they do not generally recommend email validation. However, for clients who insist on it, they recommend Kickbox.

July 2023 - Email Geeks

What the documentation says
6Technical articles

Documentation from various sources indicates that email verification and list cleaning are crucial for improving email deliverability, protecting sender reputation, reducing bounce rates, and increasing ROI. Email verification involves checking if an email address is valid and deliverable through syntax, domain, and mailbox checks. Regular list cleaning involves removing invalid, risky, and inactive email addresses. It's recommended to clean lists regularly and before sending email campaigns.

Key findings

  • Benefits of Verification: Email verification reduces bounce rates, improves deliverability, protects sender reputation, and increases ROI.
  • Verification Process: Verification involves syntax checks, domain checks, and mailbox pings.
  • List Cleaning: Regularly cleaning lists by removing invalid, risky, and inactive emails is essential.
  • Timing: Email verification and list cleaning should be done regularly and before sending campaigns.

Key considerations

  • Regularity: Implement a consistent schedule for email verification and list cleaning.
  • Tools: Consider using email verification tools to automate the process of identifying and removing invalid addresses.
  • Inactive Subscribers: Identify and remove subscribers who haven't engaged with your emails in a while.
Technical article

Documentation from SendGrid explains that maintaining good email list hygiene is crucial for improving deliverability and protecting sender reputation. They recommend regularly cleaning your list to remove invalid and inactive email addresses.

January 2022 - SendGrid.com
Technical article

Documentation from Kickbox.com explains that email verification helps reduce bounce rates, improve deliverability, protect sender reputation, and increase ROI by removing invalid and risky email addresses. They also suggest using it before sending any email campaign.

October 2024 - Kickbox.com
Technical article

Documentation from Mailchimp shares that regularly cleaning your email list helps improve deliverability, reduce bounce rates, and increase engagement rates. They recommend removing inactive subscribers and invalid email addresses.

October 2021 - Mailchimp.com
Technical article

Documentation from MailerCheck.com shares that email verification is a process of checking an email address to see if it is valid and deliverable. This is done using a range of technologies, including syntax checks, domain checks, and mailbox pings.

June 2022 - MailerCheck.com
Technical article

Documentation from Hunter.io states that using an email verification tool is a way to improve email deliverability. They suggest to clean your email list regularly to remove invalid and risky email addresses.

March 2023 - Hunter.io
Technical article

Documentation from Microsoft suggests that keeping your email lists current and accurate helps reduce the risk of your emails being marked as junk. They suggest to regularly clean your lists to remove invalid or inactive email addresses.

February 2022 - Microsoft.com