Should I send emails to a list with a high hard bounce rate and how to prevent them?
Michael Ko
Co-founder & CEO, Suped
Published 9 Jul 2025
Updated 16 Aug 2025
7 min read
Encountering a high hard bounce rate with an email list can be a frustrating experience. It signals that a significant portion of your intended recipients are unreachable due to permanent delivery failures. When you receive a warning about a substantial percentage of your list, like 12%, being hard bounces, the natural inclination might be to ignore it and send anyway, hoping for the best. However, this is a path fraught with risks to your email program's health and long-term deliverability.
I've seen many marketers face this dilemma. The immediate goal is often to reach as many people as possible, but sending to invalid email addresses actively harms your sender reputation. It's akin to repeatedly knocking on a locked door, signaling to the postal service that you're not paying attention to delivery feedback.
The impact of hard bounces on deliverability
A hard bounce occurs when an email is permanently undeliverable to an address. This could be due to the address not existing, being misspelled, or the domain name being invalid. Unlike soft bounces, which are temporary issues, hard bounces mean the email will never reach that inbox. Understanding the difference between hard and soft bounces is crucial for effective email marketing. For instance, Mailchimp describes hard bounces as a permanent reason an email cannot be delivered.
Repeatedly sending to these invalid addresses significantly damages your sender reputation. Internet Service Providers (ISPs) and mailbox providers, such as Google and Microsoft, interpret high hard bounce rates as a sign of poor list quality or, worse, spamming behavior. This can lead to your emails being directed to the spam folder, rejected entirely, or even your domain being placed on a blocklist (or blacklist).
The impact extends beyond just individual emails. A high hard bounce rate can lead to your IP address or sending domain being added to public and private blocklists (or blacklists). Being listed on a blocklist means your emails will be rejected by a wide range of recipients, severely hindering your ability to communicate effectively. This is why it's imperative to address any hard bounce warnings immediately.
Why a high hard bounce rate is a red flag
When your ESP (Email Service Provider) reports a hard bounce rate as high as 12%, it's a significant warning sign that your email acquisition methods or list management practices are flawed. Most industry experts consider a hard bounce rate above 2% to be problematic. As AgencyAnalytics notes, exceeding 2% is a red flag, indicating potential issues with list quality or the acquisition process.
Ignoring this warning means you're intentionally sending emails to addresses that you know are invalid. This practice not only wastes sending resources but also signals to mailbox providers that your sending practices are negligent or abusive. They may react by imposing stricter filtering, leading to your legitimate emails ending up in spam folders.
Another serious consequence of sending to unverified lists is hitting spam traps. These are dormant email addresses that legitimate users no longer use or addresses specifically set up by ISPs to identify spammers. Sending to a spam trap can severely damage your sender reputation and lead to immediate blacklisting (or blocklisting). Understanding how spam traps work is crucial to avoiding them.
The danger of high hard bounces
Sending to a list with a high hard bounce rate, such as 12%, is never advisable. It indicates critical issues with list hygiene and acquisition. This directly impacts your sender reputation, leading to lower inbox placement rates and potentially blacklisting (or blocklisting) by major mailbox providers. It also means you're wasting resources on addresses that will never receive your emails, negatively affecting your return on investment.
Strategies to prevent hard bounces
The best defense against hard bounces is a proactive approach to list management. This begins with how you acquire email addresses. Implementing confirmed opt-in (double opt-in) ensures that subscribers genuinely want your emails and that their email addresses are valid. For instance, Klaviyo emphasizes enabling double opt-in to ensure new subscribers truly want your content.
Another critical step is to use real-time email verification or a validation service to clean your list before sending. These services can identify and remove invalid, risky, or spam trap email addresses, preventing them from ever reaching your sending queue. While some ESPs may offer preliminary reports, a dedicated email list cleaning service can provide a more thorough scrub.
Beyond initial cleaning, regular list maintenance is key. This includes segmenting your list by engagement and removing inactive subscribers who haven't opened or clicked your emails in a long time. These contacts are more likely to become invalid over time or turn into spam traps. Here's a comparison of proactive vs. reactive approaches to managing your email list.
Proactive approach
Confirmed opt-in: Require new subscribers to verify their email address.
Real-time validation: Use a service to check email validity at the point of sign-up.
Regular hygiene: Periodically clean your list of unengaged or inactive contacts.
Impact on sender reputation
Maintains a strong and positive sender reputation. ISPs see you as a responsible sender.
Reactive approach
Single opt-in only: No email verification after initial sign-up.
No pre-send validation: Sending to all addresses, then reacting to bounces.
Infrequent cleaning: Only cleaning lists after deliverability issues arise.
Impact on sender reputation
Risks damaging sender reputation, leading to increased spam classifications and potential blocklisting (or blacklisting).
Managing an existing list with high bounces
For an existing list with a reported high hard bounce rate, the first and most critical step is to remove all hard-bounced email addresses immediately. Most ESPs will automatically suppress these, but it's important to confirm this. Continuing to send to these addresses will only exacerbate your deliverability issues and damage your sender reputation further. There's no benefit in trying to resend to them.
After removing the known hard bounces, focus on improving the quality of the remaining list. If the list is old or unengaged, consider re-engagement campaigns for the active segments. For very large, unengaged lists, you might need to adopt more aggressive cleaning strategies. Refer to steps to improve deliverability with such lists.
Regularly monitor your email deliverability metrics. Keep an eye on your bounce rates, complaint rates, and inbox placement. Tools for DMARC monitoring and blocklist monitoring can provide valuable insights into your sending health. Additionally, ensure your email authentication records, like DMARC, are correctly configured. Here's a quick example of a DMARC record.
This record, for example, tells receiving mail servers to quarantine emails that fail DMARC authentication and send aggregate reports to the specified address. Proper configuration of your DMARC record is a cornerstone of modern email security and deliverability. Regular review and optimization of these settings are part of best practices for managing bounces.
Here's a table summarizing actions for managing hard bounces:
Issue
Cause
Action to take
Prevention
High hard bounce rate
Invalid or outdated email addresses on list. Poor list acquisition methods.
Immediately remove all hard-bounced addresses. Stop sending to them permanently.
Implement double opt-in. Use real-time email verification for new sign-ups. Regularly clean your list.
Spam trap hits
Sending to old, unengaged, or purchased lists. Poor list hygiene.
Identify and remove suspicious addresses. Review list sources.
Never purchase email lists. Maintain active engagement. Regularly prune inactive subscribers.
Deliverability decline
Cumulative effect of high bounces and spam complaints over time.
Analyze bounce reports. Implement email authentication (SPF, DKIM, DMARC). Gradually increase sending volume to good segments.
Build a strong sender reputation through consistent, high-quality sending to engaged audiences.
Views from the trenches
Best practices
Always use double opt-in for new subscribers to ensure consent and validity.
Regularly validate your email lists with a reputable service to remove invalid addresses.
Segment your audience based on engagement and target active users.
Monitor your DMARC reports and bounce rates closely for early detection of issues.
Ensure your email authentication (SPF, DKIM, DMARC) is correctly configured and aligned.
Common pitfalls
Ignoring hard bounce warnings from your ESP, thinking a small number won't matter.
Sending to purchased or old, unengaged lists, which are likely to contain spam traps.
Not regularly cleaning your email list, leading to an accumulation of bad addresses.
Focusing solely on quantity of subscribers over the quality and engagement of the list.
Failing to track the source of email addresses that generate high bounces or complaints.
Expert tips
Start with smaller sends to new or re-engaged lists and slowly scale up as deliverability improves.
Identify the source of your problematic email addresses and fix the acquisition process.
A gradual approach to sending to older lists, combined with strict bounce monitoring, is safest.
Invest in email validation services before any major campaign with an unverified list.
Focus on building a highly engaged list rather than a large one with low quality.
Marketer view
A marketer from Email Geeks says that sending to a list with a 12% hard bounce rate is definitely not the smartest move, and suggests running the list through a validation service first.
January 25, 2023 - Email Geeks
Marketer view
A marketer from Email Geeks says that a 12% hard bounce rate would be a definite
January 25, 2023 - Email Geeks
Prioritizing list hygiene for long-term success
Sending emails to a list with a high hard bounce rate is a direct path to damaging your sender reputation, increasing spam folder placement, and potentially getting your domain or IP address blacklisted (or blocklisted). The short-term desire to reach every contact on a list pales in comparison to the long-term harm it inflicts on your email program.
Prioritizing list hygiene, implementing robust acquisition methods like double opt-in, and regular validation are not merely recommendations; they are essential practices for maintaining healthy email deliverability. By taking proactive steps to prevent hard bounces and swiftly addressing them when they occur, you ensure that your legitimate emails consistently reach the inbox, fostering better engagement and protecting your brand's reputation.
