Should I send emails to a list with a high hard bounce rate and how to prevent them?

Key findings

• Reputation risk: A high hard bounce rate, typically exceeding 2%, signals poor list quality to mailbox providers and can negatively impact your sender reputation, making it harder for your legitimate emails to reach the inbox. Understanding how hard bounces impact sender reputation is crucial.
• List quality: A significant hard bounce percentage indicates issues with your list acquisition or management processes.
• Immediate removal: Hard bounced addresses should be removed from your mailing list immediately to prevent further damage. Your ESP (Email Service Provider) will typically do this automatically, but it is important to verify.
• Spam trap risk: Lists with high hard bounce rates are more likely to contain spam traps, which are dormant or invalid email addresses used to identify spammers.

Key considerations

• Pre-send validation: Utilize email validation services before sending to new lists to identify and remove invalid addresses.
• Acquisition methods: Implement or review strong list acquisition practices such as double opt-in, CAPTCHA, or real-time email verification.
• Source identification: Analyze the source of your email addresses to pinpoint where low-quality leads are originating and exclude problematic sources.
• Continuous hygiene: Maintain ongoing list hygiene practices to keep your lists clean and active.

Key opinions

• Avoid sending: A 12% hard bounce rate is considered unacceptable and indicates serious list quality issues. Sending to such a list is not a smart move.
• List validation: Marketers frequently recommend using external email validation services to clean lists before attempting a send.
• Acquisition improvement: High bounce rates suggest fundamental problems with how email addresses are being collected, necessitating a review of acquisition methods.
• Spam trap avoidance: Even after removing invalid emails, a poorly sourced list might still contain dangerous spam traps, which can lead to blacklisting.

Key considerations

• List source: Investigate the origin of the problematic email addresses. Identifying and excluding bad sources is a key long-term strategy.
• Quality over quantity: Even small numbers of known bounces pose a risk to deliverability. Prioritize a clean, engaged list over a large, unverified one.
• Long-term hygiene: Relying on list hygiene and good data collection practices is fundamental for sustainable email marketing success. Implementing double opt-in is a strong step.
• Engagement first: If a cleaned list still shows low engagement, consider whether further communication is worthwhile, as sending to unreactive contacts is often unproductive.

Key opinions

• Reputation damage: High hard bounce rates are a strong indicator of low list quality, which directly harms your sender reputation. ISPs interpret this as irresponsible sending behavior.
• Spam trap risk: Lists with high hard bounces are likely to contain spam traps, which are a critical threat to deliverability and can lead to immediate blacklisting.
• Avoid purchased lists: Experts strongly advise against using purchased or scraped email lists, as these are primary sources of high hard bounces and spam traps.
• Proactive cleaning: It is essential to clean lists before sending, even if your ESP has automatic suppression. Preventing bounces upfront is always better than reacting to them.

Key considerations

• Authentication: Properly authenticating your email domain with SPF, DKIM, and DMARC can help protect your sender reputation when dealing with list quality issues.
• Engagement strategy: Beyond bounce rates, monitor engagement metrics. Low engagement on a list, even after cleaning, suggests it may not be worth emailing.
• Gradual sending: For older or questionable lists, consider segmenting and sending to smaller, more engaged subsets first to gauge performance and minimize risk.
• Domain reputation: A high hard bounce rate directly impacts your email domain reputation. Regular monitoring is essential.

Key findings

• Sender reputation impact: Mailbox providers view high hard bounce rates negatively because they indicate poor address collection or list management processes.
• Thresholds: Generally, a hard bounce rate above 2% is considered problematic and a clear sign of list quality issues.
• Automatic suppression: Email service providers often automatically suppress hard bounced addresses to protect their shared IP reputation, but this should not be a substitute for sender-side list cleaning.
• Spam indicators: High bounce rates, especially hard bounces, are frequently linked to the presence of spam traps or outdated data, which can lead to emails being flagged as spam.

Key considerations

• Authentication: To mitigate the impact of bounces and improve overall deliverability, proper domain authentication with SPF, DKIM, and DMARC is strongly recommended.
• List cleaning: Regularly cleaning email lists by removing hard bounces and unengaged subscribers is a fundamental deliverability best practice. This also includes managing soft bounces.
• Consent: Ensuring email addresses are real, consented profiles through methods like double opt-in is paramount for minimizing bounce rates and maintaining a healthy list.
• Monitoring: Continuously monitor your bounce rates and other deliverability metrics to identify issues early and take corrective action, improving your overall email deliverability.