A bounce is an email that never reaches the recipient. A hard bounce is permanent (the address doesn't exist); a soft bounce is temporary (the mailbox is full).
Why bounce rates climb
- Old, unverified lists
- Purchased addresses
- Typos in the data (think gmial.com)
How to bring it down
Verify your list before you send: MX and SMTP checks, typo detection, and spam-trap cleanup weed out the invalid addresses. We consistently see bounce rates drop sharply once Qulaq verification is in the loop.