What is Bounce Rate?
Bounce rate in email refers to the percentage of sent emails that could not be delivered to the recipient's mailbox, categorized as either hard bounces (permanent failures) or soft bounces (temporary issues).
Bounce rate is a critical email delivery metric that measures the percentage of emails that fail to reach their intended recipients. It is calculated as the number of bounced emails divided by the total number of emails sent, expressed as a percentage. Bounces are classified into two categories: hard bounces and soft bounces, each with different implications for your email program.
Hard bounces are permanent delivery failures. They occur when an email address does not exist, the domain is invalid, or the recipient's mail server has permanently rejected the message. Hard bounces are the most damaging type because they signal to email providers that you are sending to unverified or purchased lists. Common causes include outdated addresses where the person has left the company, typos in email addresses, or addresses from companies that have shut down.
Soft bounces are temporary delivery failures. They happen when the recipient's mailbox is full, the mail server is temporarily unavailable, the message is too large, or the server is rate-limiting incoming connections. Soft bounces may resolve on their own - most email systems will retry delivery several times before giving up. However, persistent soft bounces on the same address may indicate a deeper problem.
The impact of high bounce rates on B2B operations is severe. Email service providers monitor bounce rates closely. When your bounce rate exceeds 2-3%, providers like Google and Microsoft begin to treat your domain as potentially spammy, reducing deliverability for all your emails - including legitimate sales conversations. Getting off a blocklist or rebuilding sender reputation can take weeks or months.
Preventing bounces starts with list hygiene. Cleanlist helps teams maintain low bounce rates by verifying email addresses before they are used in outreach. Every email processed through the platform is checked for validity, and addresses that would cause hard bounces are flagged before they ever reach your sending infrastructure. For existing databases, Cleanlist can run batch verification to identify and remove addresses that have gone stale since they were last used, preventing bounce rate spikes when launching campaigns against older lists.
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See how Cleanlist handles bounce rate →Frequently Asked Questions
What is an acceptable email bounce rate?
For B2B email campaigns, an acceptable bounce rate is below 2%. Best-in-class programs maintain bounce rates under 1%. Hard bounces specifically should be below 0.5%. If your bounce rate exceeds 3%, most email providers will begin throttling your deliverability. Consistently high bounce rates can result in your domain being blacklisted entirely.
What is the difference between a hard bounce and a soft bounce?
A hard bounce is a permanent delivery failure - the email address does not exist, the domain is invalid, or the server has permanently rejected your message. Hard bounces should trigger immediate removal of the address from your list. A soft bounce is a temporary failure - the mailbox is full, the server is down, or there is a rate limit. Soft bounces may resolve on retry, but persistent soft bounces should be investigated.
How do I reduce my email bounce rate?
The most effective approach is to verify all email addresses before sending. Use an email verification service like Cleanlist to check addresses in bulk before campaigns. Additionally, implement real-time verification on web forms to prevent invalid addresses from entering your system, remove contacts who have not engaged in 6+ months, and re-verify your database quarterly to catch addresses that have become invalid due to job changes.
Related Terms
Email Verification
Email verification is the process of confirming that an email address is valid, properly formatted, and capable of receiving messages, without actually sending an email.
Deliverability Score
A deliverability score is a rating that predicts how likely an email is to successfully reach the recipient's inbox rather than being filtered to spam or bounced.
Data Decay
Data decay is the gradual degradation of data accuracy over time as contact details, job titles, company information, and other B2B data points become outdated.