Email bounce rate is the percentage of sent emails that fail to reach the recipient's inbox. A "hard bounce" means the address doesn't exist or the domain is invalid. A "soft bounce" means the mailbox is temporarily full, the server is down, or the message was too large. ISPs track your bounce rate and use it to decide whether to deliver your future emails or send them to spam.
Why It Matters
ISPs like Gmail and Outlook watch your bounce rate closely. Send to too many bad addresses and your sender reputation drops, which means even your emails to valid addresses start landing in spam. Most email platforms will suspend your account if your bounce rate exceeds 5%. A single bad campaign to an uncleaned list can damage your deliverability for weeks.
How to Reduce Bounce Rates
- Verify before sending: Run your list through email verification to catch invalid addresses before they bounce
- Remove hard bounces immediately: Never send to an address that hard-bounced. It won't suddenly start working
- Monitor soft bounces: Retry soft bounces once or twice, then remove them if they keep failing
- Clean on a schedule: B2B email lists decay at 2-3% per month. Quarterly cleaning prevents accumulation
- Use double opt-in: For inbound lists, confirm the email address works before adding it to your database
Example
A sales team sends 5,000 cold emails and gets a 12% bounce rate. Their email provider flags the account. Deliverability drops from 95% to 60% across all campaigns for the next three weeks. They clean the list, remove 800 bad addresses, and slowly rebuild their sender score over the following month.
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