Why Emails Bounce (and How to Stop It)
A bounce happens when an email can't be delivered and the receiving server sends it back. A few bounces are normal. A lot of them is a warning sign to email providers, and a high bounce rate can hurt the delivery of everything else you send.
Hard bounces vs. soft bounces
| Hard bounce | Soft bounce | |
|---|---|---|
| What it means | Permanent failure. The email can never be delivered to this address. | Temporary failure. Delivery might work later. |
| Common causes | The address or domain doesn't exist, or the domain has no mail servers. | Full mailbox, server temporarily down, or message too large. |
| What to do | Remove the address right away. | Retry; remove it if it keeps soft-bouncing. |
The most common reasons emails bounce
1. The address doesn't exist
The person left the company, closed the account, or the address never existed. This is the classic hard bounce.
2. Typos in the address
gmial.com, yahoo.con, hotmial.com: small typos on signup forms create addresses that bounce every time. Many can be fixed rather than deleted.
3. The domain is dead or can't receive email
Companies close, rebrand and let domains expire. If a domain no longer exists, or has no mail servers set up, every address on it will hard-bounce.
4. Disposable addresses that have expired
Temporary inboxes vanish quickly, so emails sent later fail. See What is a disposable email address?
5. Full or temporarily unavailable mailboxes
These cause soft bounces. They often clear up on their own, but an inbox that stays full for weeks is probably abandoned.
6. The receiving server blocks you
Sometimes the address is fine but the receiving server refuses your message, for example because of your sending reputation or missing email authentication (SPF, DKIM and DMARC). Major providers like Gmail and Yahoo now require bulk senders to authenticate their email.
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How to lower your bounce rate
- Clean your list before you send. Remove broken addresses, dead domains, typos and disposable inboxes. Our step-by-step guide shows how: How to clean an email list.
- Use double opt-in. A confirmation email proves the address works and belongs to someone who wants your emails.
- Remove hard bounces immediately. Never keep sending to an address that has hard-bounced.
- Re-check old lists. A list you haven't emailed in months needs cleaning before you use it again.
- Set up email authentication. Make sure SPF, DKIM and DMARC are configured for your sending domain.
- Never buy lists. Purchased lists are full of dead and unwilling addresses, and they're a fast way to damage your reputation.
What's a good bounce rate?
Lower is always better. As a general guide, many email platforms suggest keeping your bounce rate under about 2%, and a well-maintained list usually does much better than that. If you see a sudden jump, pause and clean your list before sending again.
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Frequently asked questions
What is the difference between a hard and soft bounce?
A hard bounce is permanent: the address or domain can't receive email, so remove it. A soft bounce is temporary, such as a full mailbox, and may succeed later.
What is a good email bounce rate?
As low as possible. Many email platforms suggest staying under about 2%.
Can I prevent all bounces?
Not completely. Cleaning your list removes most causes of hard bounces, but some addresses go dead between checks, so always remove addresses that hard-bounce after a send.