Glossary
Bounce Rate — Hard vs Soft Bounces
Bounce rate is the percentage of emails that could not be delivered — split into hard bounces (permanent: bad address, domain doesn’t exist) and soft bounces (temporary: mailbox full, server timeout). High bounce rates damage sender reputation and can trigger blacklistings.
Why operators track it
Mailbox providers use bounce rate as a hygiene signal. A sudden spike in hard bounces often means a scraped or purchased list — not an accident.
What to do
Suppress hard-bounce addresses immediately. Retry soft bounces per ESP policy — then remove chronic soft bounces.
FAQ
What is a hard bounce?
A permanent failure — invalid recipient, unknown domain, or policy block. Remove the address from your list.
What is a soft bounce?
Temporary — full mailbox, greylisting, or server busy. May retry; suppress if it persists.
How does bounce rate affect deliverability?
High hard bounces hurt IP and domain reputation — receivers may throttle or block you.