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A hard bounce is a permanent email delivery failure that occurs when an email cannot be delivered due to a permanent reason, such as an invalid email address, non-existent domain, or blocked recipient. Hard bounces should be removed from your list immediately.
Invalid or misspelled email addresses (john@gmial.com)
Non-existent domains (user@companythatclosed.com)
Deleted or deactivated email accounts
Blocked recipients who have marked you as spam
Typos in the domain name or username
Hard bounces directly damage your sender reputation. Email providers track your bounce rate, and high rates signal that you're not maintaining a quality list. A bounce rate above 2% is concerning, and above 5% can result in blacklisting. Each hard bounce is a warning sign that needs immediate action.
Remove hard bounces from your list immediately after each campaign
Never send to an address that has hard bounced
Verify email addresses at the point of collection
Use email verification services to clean your list proactively
Monitor bounce rates and investigate sudden spikes
Hard bounces are permanent failures (invalid addresses, non-existent domains) that require immediate removal. Soft bounces are temporary issues (full inbox, server down) that may resolve on their own. After 3-5 consecutive soft bounces, treat them as hard bounces.
Keep hard bounce rates below 0.5% per campaign. If you're seeing rates above 2%, you have a list quality problem. Regular email verification can reduce hard bounces to near zero.
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