What should I do if a user's email hard bounced and they aren't receiving emails?
Michael Ko
Co-founder & CEO, Suped
Published 11 Jun 2025
Updated 16 Aug 2025
9 min read
It is frustrating when a valuable user reaches out, asking why they haven't received your emails, only to discover their email hard bounced months ago. A hard bounce signifies a permanent delivery failure, meaning the recipient's mail server has completely rejected your email for a reason it considers unresolvable. This usually leads to the email address being automatically added to your suppression list, preventing future delivery attempts.
When a hard bounce occurs, it can severely impact your sender reputation, leading to lower inbox placement rates for all your emails. More importantly, it means a critical communication breakdown with a customer. Resolving this requires a multi-faceted approach, focusing on diagnostics, user communication, and preventative measures.
Understanding hard bounces and their impact
The first step is to accurately diagnose why the hard bounce occurred. Even a seemingly valid email address, like a Gmail.com address, can hard bounce for various reasons. These include an invalid email address (e.g., typos, deleted accounts), the domain not existing, or the recipient's mail server blocking the email due to perceived spam or a strict security policy. Your email service provider (ESP) should provide bounce logs or reports that detail the specific reason and error code.
Hard bounces are permanent failures and differ significantly from soft bounces, which are temporary. My guide explains how hard and soft bounces are defined. Most ESPs automatically add hard bounced addresses to a suppression list to protect your sender reputation, preventing you from sending to them again. This is a crucial protective measure, but it means you need a clear process to address legitimate users caught in this net.
A common scenario is when a user's mailbox was full or inactive previously, leading to a hard bounce designation. However, they may have since cleared their inbox or reactivated their account. Understanding these nuances is key, as simply assuming the address is permanently dead can lead to lost customer engagement. You can learn more about common bounce reasons in this email bounces guide from Postmark.
Initial troubleshooting steps
Once you've identified a hard bounced email address belonging to a legitimate user, your immediate goal is to re-establish communication. The first step is always to communicate directly with the user, ideally through an alternative channel like phone or live chat, to verify their preferred email address. This ensures you're not trying to force emails to an address that genuinely no longer exists or is incorrect.
If the user confirms the email address is correct and should be receiving emails, you'll need to manually remove it from your ESP's suppression or hard bounce list. This process varies by provider. Some ESPs allow direct removal, while others require a support ticket. Be cautious and only do this for confirmed, active users, as repeatedly sending to invalid addresses can harm your sender reputation.
For Gmail addresses, there are a couple of tricks users can employ to receive emails, even if their primary address was suppressed. The 'dot trick' involves adding or removing dots in their Gmail username (e.g., john.doe@gmail.com vs. johndoe@gmail.com). The 'plus trick' involves adding a plus sign and any word before the @ symbol (e.g., john.doe+newsletter@gmail.com). While these appear as new addresses to your ESP, they all deliver to the user's original Gmail inbox. For more specific Gmailtroubleshooting steps, check Google's support.
Addressing underlying deliverability issues
A persistent hard bounce issue, even for seemingly valid addresses, can point to broader deliverability problems affecting your sender reputation. Internet Service Providers (ISPs) and mailbox providers (like Outlook and Yahoo) scrutinize sending practices. High hard bounce rates signal poor list hygiene or potentially malicious activity, leading to stricter filtering or even placing your sending IP or domain on a blocklist (or blacklist).
Ensure your email authentication protocols, such as SPF, DKIM, and DMARC, are correctly configured. These records prove your emails are legitimate and prevent spoofing, which significantly boosts your sender reputation. A simple guide to DMARC, SPF, and DKIM can help you set them up. ISPs are increasingly strict, and misconfigurations can cause legitimate emails to bounce or land in spam folders. You can also refer to this Spamhaus guide on managing bounces for more insights.
If a sudden increase in hard bounces affects multiple users, it might indicate a larger issue with your sending practices or a temporary block on your sending domain or IP. Checking various email blocklists (blacklists) can help determine if your reputation is under attack. Understanding how to troubleshoot email bounce messages is crucial for quick resolution. Sometimes, deliverable users might still experience hard bounces; my article explains why deliverable users get hard bounces.
Long-term strategies for prevention
To prevent future hard bounces and maintain a healthy sender reputation, consistent list hygiene is non-negotiable. Regularly clean your email lists by removing invalid or inactive addresses. This practice significantly reduces your hard bounce rate and protects your domain. Implement a double opt-in process for new subscribers to ensure that only engaged, valid email addresses are added to your lists.
Monitor your hard bounce rates closely. Most ESPs provide dashboards or reports that show these metrics. A sudden spike can indicate an issue that needs immediate attention. Proactive monitoring helps you catch problems before they escalate and impact a large portion of your audience. Managing these bounces effectively is part of the best practices for managing hard and soft bounces.
Consider implementing a re-engagement strategy for inactive users before removing them. If emails to these segments consistently hard bounce, it's safer for your reputation to remove them from your active sending lists. My article on sending to lists with high hard bounce rates offers more guidance. Regularly reviewing your email database helps ensure you are only sending to engaged and valid contacts, which is crucial for overall email deliverability.
Views from the trenches
Clear suppression list: When a legitimate user reports not receiving emails due to a hard bounce, manually remove their address from your ESP's suppression list.
Verify with user: Always confirm the correct email address with the user directly, preferably through an alternative contact method.
Gmail dot/plus trick: For Gmail users, suggest they try a variation of their email address using dots or plus signs if their original address is suppressed.
Ignoring suppression lists: Not checking or managing your ESP's suppression list means legitimate users might remain unreached.
No direct communication: Failing to reach out to the user via other channels misses an opportunity to verify the email and re-engage them.
Assuming permanent invalidity: Assuming a hard bounced address is always permanently invalid without verification can lead to losing valuable contacts.
Automate suppression management: Explore workflows in your ESP to automatically re-engage or re-add confirmed valid addresses that were previously suppressed.
Educate users on email variations: Inform users about Gmail's dot and plus addressing features, empowering them to self-resolve some delivery issues.
Marketer from Email Geeks says clearing the email from the suppression list is often the quickest solution.
Marketer from Email Geeks says asking the user to reconfirm their email address or providing a new one can resolve issues, especially if there was a typo.
Expert from Email Geeks says that for Gmail addresses, suggesting the user try the 'dot trick' allows them to register a seemingly new address with the ESP, while still receiving emails at their original Gmail inbox.
Marketer from Email Geeks says the 'plus trick' with Gmail addresses (adding +something before the @) can also work to bypass ESP suppression.
Marketer from Email Geeks says that in Iterable, hard bounced addresses are typically unsubscribed from channels, but can be manually re-added or automatically re-engaged through a workflow.
Ensuring email continuity
Addressing hard bounces for individual users is a critical task for maintaining customer satisfaction and healthy email deliverability. It requires a blend of direct user communication, careful management of your ESP's suppression lists, and an understanding of underlying email authentication and reputation factors. While one-off issues can be resolved with direct intervention, consistent monitoring and proactive list hygiene are essential to prevent widespread problems.
Remember, every hard bounce is an opportunity to improve your sending practices. By troubleshooting effectively and implementing preventative measures, you can ensure your important messages reach their intended recipients, safeguarding both your sender reputation and customer relationships.
Gmail.com address, can hard bounce for various reasons. These include an invalid email address (e.g., typos, deleted accounts), the domain not existing, or the recipient's mail server blocking the email due to perceived spam or a strict security policy. Your email service provider (ESP) should provide bounce logs or reports that detail the specific reason and error code.
Gmail username (e.g., john.doe@gmail.com vs. johndoe@gmail.com). The 'plus trick' involves adding a plus sign and any word before the @ symbol (e.g., john.doe+newsletter@gmail.com). While these appear as new addresses to your ESP, they all deliver to the user's original Gmail inbox. For more specific Gmailtroubleshooting steps, check Google's support.
Outlook and 
Yahoo) scrutinize sending practices. High hard bounce rates signal poor list hygiene or potentially malicious activity, leading to stricter filtering or even placing your sending IP or domain on a blocklist (or blacklist).
