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Summary

Managing hard bounced email addresses is critical for maintaining a healthy sender reputation and ensuring email deliverability. A hard bounce signifies a permanent delivery failure, meaning the email address is invalid, nonexistent, or blocked indefinitely. Continuing to send to such addresses can severely harm your sender score, leading to increased spam classifications and even blocklisting. This summary consolidates insights from deliverability professionals, email marketers, and industry documentation on best practices for handling hard bounces, emphasizing immediate suppression for marketing lists and a more nuanced approach for transactional communications.

What email marketers say

Email marketers generally agree on the importance of suppressing hard bounces immediately for marketing purposes, but opinions vary slightly when it comes to transactional emails and the potential for a hard bounced address to become deliverable again. The consensus is that preserving sender reputation outweighs the slim chance of re-engaging a permanently failed address.

Marketer view

A marketer from Email Geeks states that they suppress hard bounced email addresses indefinitely on the account until a user explicitly requests to be removed or re-added. This strategy aims for a clear and permanent solution to invalid addresses. They acknowledge a differing viewpoint that these addresses could become deliverable after a certain period, but they prioritize avoiding repeated sends to bad addresses.

26 Jul 2019 - Email Geeks

Marketer view

A marketer from Email Geeks agrees with indefinite suppression, citing the difficulty of knowing if a re-deliverable address belongs to the same person. Maintaining a clean list by avoiding unknown recipients is paramount for deliverability.

26 Jul 2019 - Email Geeks

What the experts say

Deliverability experts generally agree that hard bounces indicate a permanent issue and require immediate suppression to protect sender reputation. Discussions often revolve around the nuances of bounce error messages, the reality of recycled spam traps, and the strategic differences between managing marketing and transactional hard bounces. The consensus leans heavily towards proactive list hygiene and careful judgment for exceptions.

Expert view

An expert from Email Geeks notes that the approach to handling hard bounces depends heavily on the specific definition of 'hard bounce' and the context of its occurrence. This suggests that a one-size-fits-all solution might not be optimal for all sending scenarios.

26 Jul 2019 - Email Geeks

Expert view

An expert from Email Geeks suggests that if an email is rejected at least three times over a minimum of fourteen days, it should be suppressed until the owner actively re-subscribes. They also acknowledge that more aggressive approaches, such as immediate suppression after a single bounce, are acceptable depending on the sender's risk tolerance.

26 Jul 2019 - Email Geeks

What the documentation says

Official documentation from various email service providers consistently advises prompt action on hard bounces to maintain good sending hygiene and protect sender reputation. These platforms often automate the suppression of hard bounces, underlining the severity of these delivery failures. The documentation generally differentiates between hard and soft bounces, with hard bounces requiring permanent removal from active lists.

Technical article

Documentation from Mailchimp explains that a hard bounce signifies a permanent reason an email cannot be delivered. In the majority of cases, email addresses that hard bounce are automatically removed or 'cleaned' from your audience lists by their system. This automated process is designed to help maintain list health.

22 Mar 2025 - Mailchimp

Technical article

Documentation from Klaviyo confirms that their platform automatically suppresses emails that hard bounce. These suppressed addresses are then excluded from future email sends, ensuring that users do not repeatedly target invalid contacts and protecting sender reputation. Users can typically view these suppressed addresses within their account settings.

22 Mar 2025 - Klaviyo Help Center

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    How to manage hard bounced email addresses for future sends? - Troubleshooting - Email deliverability - Knowledge base - Suped