Hard Bounce / Email Marketing Terms Hard Bounce A hard bounce is a type of email delivery failure that occurs when a message is permanently rejected by the recipient’s email server. This usually happens because the email address is invalid, does not exist, is misspelled, or the domain no longer accepts email. Unlike a soft bounce, which is temporary and may be resolved later, a hard bounce signals a definitive delivery problem. Most email marketing platforms will automatically flag or suppress hard-bounced addresses to protect your sender reputation. Common causes of hard bounces include typos in the email address (such as john@gnail.com), expired domains, or deleted inboxes. Some email addresses may also return hard bounces if they were once valid but have since been deactivated. Email marketing services like Mailchimp, HubSpot and Constant Contact track bounce data and recommend removing or suppressing hard-bounced contacts after a campaign. Continuing to send to these addresses can lower your deliverability rates and risk getting flagged as spam. Maintaining a clean email list by regularly checking for hard bounces helps protect your sender score and ensures your messages reach real users. A high hard bounce rate may suggest issues with list quality, such as purchased lists, outdated contacts or lack of double opt-in verification. For nonprofits, SaaS providers and B2B marketers, good email hygiene supports trust, engagement and campaign performance. Reviewing bounce reports after each campaign helps identify trends and take action before they impact future sends.