In email marketing, bounce rate is the percentage of emails that were not successfully delivered to recipients’ inboxes. When an email “bounces,” it means the receiving server rejected it or couldn’t accept it. Bounce rate is a key deliverability metric because it reflects the health of your email list and can influence your sender reputation over time.
Bounce rate is typically calculated as:
Bounce rate (%) = (Bounced emails ÷ Emails sent) × 100
For example, if you send 10,000 emails and 200 bounce, your bounce rate is 2%.
Why bounce rate matters
A high bounce rate can indicate poor list quality, outdated contacts, or technical issues with your sending practices. Mailbox providers track bounce behavior because it helps them identify senders who might be sending to invalid addresses or using questionable list sources.
A consistently high bounce rate can lead to:
- Lower inbox placement (more emails going to spam)
- Reduced sender reputation
- Higher likelihood of account review by your email service provider
- Wasted sending volume and skewed reporting
Types of bounces: hard vs. soft
Not all bounces are the same. The two main categories are hard bounces and soft bounces.
Hard bounce (permanent failure)
A hard bounce means the email cannot be delivered due to a permanent reason, such as:
- The email address doesn’t exist
- The domain name is invalid
- The recipient server rejects all mail for that address
Hard bounces should be removed from your list immediately. Continuing to send to hard-bounced addresses hurts deliverability and increases the chance of being flagged as a low-quality sender.
Soft bounce (temporary failure)
A soft bounce is a temporary delivery issue, such as:
- The recipient inbox is full
- The recipient server is temporarily unavailable
- The message is too large
- Temporary rate limiting or filtering
Soft bounces may resolve on their own, but repeated soft bounces can become a sign that the address is no longer active or that your sending is being throttled.
Common causes of high bounce rate
Bounce rate usually rises due to list or acquisition problems. Common causes include:
1) Old or purchased lists
Purchased lists often contain invalid, outdated, or non-consenting addresses. This leads to high bounce rates and complaints.
2) Poor list hygiene
If you don’t remove inactive or invalid addresses over time, bounces increase naturally.
3) Typos at signup
Mistyped addresses (like “gmial.com”) are a major source of hard bounces.
4) Sudden list growth
If you import a large batch of contacts without verifying them, bounce rate may spike.
5) Deliverability issues
Sometimes a bounce is related to authentication problems (SPF, DKIM, DMARC), reputation issues, or server policies.
How to reduce bounce rate
Reducing bounce rate starts with better data quality and permission-based acquisition.
Use double opt-in
Double opt-in confirms that the address is real and that the person wants to receive emails. It’s one of the most effective ways to reduce invalid signups.
Validate email addresses
Use real-time validation on forms to catch typos and fake addresses before they enter your list.
Remove hard bounces automatically
Most email marketing platforms suppress hard bounces automatically. Ensure this is enabled and never re-add those contacts.
Clean your list regularly
Identify and remove:
- Inactive subscribers who never engage
- Repeated soft bounces
- Old addresses from legacy imports
Warm up new sending domains
If you’re sending from a new domain or IP, gradually increase volume to build trust with mailbox providers.
What is a “good” bounce rate?
Bounce rate benchmarks vary, but many email marketers aim for under 2%, with under 1% being ideal for well-maintained lists. The best benchmark is your own historical performance—watch for spikes and trends.
Key takeaway
Bounce rate measures how many emails fail to reach recipients. Keeping bounce rate low improves deliverability, protects your sender reputation, and ensures you’re sending to real people who can actually receive your messages.