An email bounce occurs when an email cannot be delivered to the intended recipient and the receiving mail server rejects or returns the message. The reason for the failure is usually provided through an SMTP response or bounce code.
There are two main types of email bounces:
- Soft bounce: A temporary delivery failure. Common causes include a full recipient mailbox, temporary server issues, message size limits, or temporary delivery restrictions.
- Hard bounce: A permanent delivery failure. Common causes include an invalid, non-existent, or deactivated email address.
What Happens When an Email Bounces?
After a bounce occurs, the sending system records the delivery failure and may provide a bounce code indicating the reason. Temporary failures may be retried, whereas permanent failures generally require that the address be removed or suppressed from future sends.
Why Are Email Bounces Important?
A high number of bounces can indicate problems with email data quality or sending practices. Repeatedly sending messages to invalid or undeliverable addresses can negatively affect sender reputation and email deliverability.
Bounce rate measures the percentage of sent emails that result in a bounce. Monitoring bounce rates and bounce codes can help identify recurring delivery problems and their likely causes.
How Can You Reduce Email Bounces?
Maintaining accurate email data can help reduce avoidable bounces. Email verification can identify invalid or undeliverable addresses before they are added to a campaign or mailing list. Regular list maintenance can also help identify addresses that have become invalid and should no longer receive emails.