Bounce Email
A bounce email is an email that was not delivered to the recipient and was returned to the sender with a delivery error notification.
Simply put:
An email that did not reach the recipient
Why emails bounce
Main reasons:
- Incorrect email address
- Non‑existent mailbox
- Recipient’s mailbox is full
- Sender is blocked
- Technical errors on the mail server
- Domain reputation issues
Types of bounce emails
Hard Bounce
The email cannot be delivered.
Reasons:
- The address does not exist
- The domain has been removed
- An error in the email address
Example: user@example.com no longer exists.
Such addresses are usually removed from the database.
Soft Bounce
A temporary delivery issue.
Reasons:
- Mailbox is full
- The server is temporarily unavailable
- The email is too large
A retry may succeed.
Where the term is used
- Email marketing
- CRM marketing
- Automated email campaigns
- Transactional emails
- Bulk email sending systems
Why it’s important to track bounces
A high number of bounce emails can lead to:
- Lower deliverability
- Poor domain reputation
- Being marked as spam
- Email sending being blocked
Metrics
Bounce Rate
Shows the percentage of undelivered emails.
Formula:
Bounce Rate = (Number of bounces ÷ Number of sent emails) × 100%
How to reduce bounce rates
- Regularly clean your email list
- Use double opt‑in
- Verify addresses before sending
- Remove inactive and invalid contacts
- Monitor domain and IP reputation
Example
A company sends 10,000 emails.
200 emails are not delivered due to non‑existent addresses.
Bounce Rate = 2%
Those 200 addresses should be checked or removed from the database.
Key takeaway
A bounce email is an email that could not be delivered to the recipient and was returned to the sender with an error message. Monitoring bounces helps maintain email list quality, high deliverability, and the effectiveness of email marketing.
