What is an email bounce?
Quick answer
An email bounce is a message that comes back undelivered. A hard bounce is permanent, such as an address that does not exist or a domain that has expired. A soft bounce is temporary, such as a full mailbox. The bounce rate is the share of a send that bounced, and email services watch it closely.
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Updated · By Robert Breen
Why it matters for a small business
Bounces are a signal to mailbox providers. If you keep sending to addresses that do not exist, you look like a sender who does not check their list, and providers can respond by sending more of your mail to spam. That is a deliverability problem, and it affects the good addresses on your list too, not only the dead ones.
It is also a cost problem. Many email services charge by contact, so a list with old addresses costs money every month. And it is a quiet problem: you rarely see a warning until the bounce rate on a report is already high.
Hard bounce vs soft bounce
| Type | What it means | What to do |
|---|---|---|
| Hard bounce | Permanent: the address does not exist, has a typo or the domain is gone | Remove it from the list and do not send again |
| Soft bounce | Temporary: the mailbox is full or the server is down for a while | Try again later, and remove it if it keeps failing |
Email services set their own bounce limits and warnings, so check your provider's rules instead of relying on a single number.
In a real lesson: Protect Your Sender Reputation Before a Big Send using no2bounce
In the no2bounce lesson, Nora markets a made-up event space, Lantern Hill Venue. Her open house invitation went to 600 contacts and 54 bounced, which is 9%. The numbers are an illustration, not a benchmark, but they show the problem: the list was built over years from badge scans and old sign-ups.
The lesson checks a 30-row contact list before the next send. The list includes typos such as gmial.com and a .con ending, shared inboxes and a former employee. You upload it, read the Deliverable, Risky and UnDeliverable groups, and download only the confirmed addresses. A message to that file should not hard bounce.
Try this lesson free or read the step-by-step guide.
Common confusions
Bounce vs spam folder
A bounce means the message was refused or could not be delivered. A message in the spam folder was delivered, just not to the inbox.
Bounce vs unsubscribe
An unsubscribe is a person choosing to stop. A bounce is a technical failure. Honor both, and never send again to either.
Tips
- Check a list that is more than a few months old before a big send.
- Watch the bounce rate on every report and act early.
- Only email people who have a reason to hear from you, and follow the opt-in and unsubscribe rules where you send.
Related terms
More Business terms
Where you use it: free lessons
- Protect Your Sender Reputation Before a Big Send using no2bounce (no2bounce, 8 min)
Prompt templates that use it
Frequently asked questions
- What is the difference between a hard and a soft bounce?
- A hard bounce is permanent, like an address that does not exist. A soft bounce is temporary, like a full mailbox. Remove hard bounces right away.
- What is a good bounce rate?
- Lower is better. Providers often suggest keeping it low, commonly cited at around 2% or less, but each email service sets its own limits, so check yours.
- How do I reduce email bounces?
- Check your list with an email verifier before a big send, remove hard bounces after each campaign, and collect addresses with a confirmation step.