Glossary
Email bounce rate
Email bounce rate is the share of sent emails that receiving servers returned as undeliverable. Hard bounces are permanent, such as a nonexistent address. Soft bounces are temporary, such as a full mailbox or a server that is down.
What Is Email Bounce Rate?
In short When delivery fails, the receiving server answers with a status code.
RFC 3463 defines the enhanced codes: a first digit of 5 is a permanent failure, such as 5.1.1 for a mailbox that does not exist, and a first digit of 4 is a temporary one, such as 4.2.2 for a full mailbox. Permanent failures are hard bounces. Temporary ones are soft bounces, and the sending server retries for a while before giving up.
Bounces are one of the clearest signals mailbox providers get about list quality. A sender that keeps hitting nonexistent addresses looks like someone using a bought or scraped list, and its later mail gets filtered harder. Remove hard bounces at once, and stop sending from a domain whose bounce rate keeps climbing until you find the cause.
Email Bounce Rate Example
Bounce rate = bounced emails / sent emails x 100Example: a campaign sends 2,000 emails. 30 come back with 550 5.1.1 (mailbox does not exist) and 10 with 452 4.2.2 (mailbox full). Bounce rate is 40 / 2,000 x 100 = 2%, and the hard bounce rate is 1.5%. The 30 addresses come off the list, and the 10 get another try next week.
Email Bounce Rate in Practice
Measure it per campaign and per sending domain, against emails sent, and track hard bounces on their own. Read the codes, not just the count: a 550 can also be a policy block rather than a missing mailbox, and a few soft bounces during a provider outage are normal.
FAQ
How do you calculate email bounce rate?
Divide bounced emails by emails sent and multiply by 100. 40 bounces out of 2,000 sends is a 2% bounce rate.
What is a good email bounce rate?
There is no industry standard. Twilio SendGrid recommends keeping hard bounces under 5% of attempted messages. Ken's view: a verified cold email list should bounce well below that, and a sending domain above 3% needs a look before it sends more.
What is the difference between a hard bounce and a soft bounce?
A hard bounce is a permanent failure, such as an address that does not exist, and RFC 3463 codes it with a first digit of 5. A soft bounce is temporary, such as a full mailbox, coded with a 4. Remove hard bounces from your list and retry soft bounces later.
What causes a high email bounce rate?
Old or unverified lists, guessed email patterns, typos, catch-all domains that reject mail later and disposable addresses. In B2B the biggest cause is job changes: an address that worked last year belonged to someone who has since left.
Is email bounce rate the same as website bounce rate?
No. Email bounce rate counts messages that could not be delivered. In Google Analytics 4, bounce rate is the percentage of website sessions that were not engaged. The two share a name and nothing else.
Do This in Ken
Do This in Ken
Campaigns reports bounce rate for every campaign, and Ken Search charges 1 credit only for emails that verify as valid, which keeps hard bounces down from the first send.
- Module
- Campaigns
- Open in Ken
- /features
The new Ken opens to the waiting list in batches.
Related
- GTM Glossary
Every GTM term, grouped by topic.
- Email verification
- Catch-all email
- Sender reputation
- Email open rate
- Ken
Sources
| Source | Checked |
|---|---|
| RFC 3463: Enhanced Mail System Status Codes | |
| Twilio SendGrid Docs: Bounce and block classifications | |
| Google Analytics Help: Engagement rate and bounce rate |
Changelog
- Page published.