Hard vs soft
A hard bounce means the address does not exist or the domain is invalid, permanent and reputation-damaging. A soft bounce is temporary, a full mailbox or a server briefly down. Hard bounces are the ones mailbox providers read as the signature of an unverified list. Why a high bounce rate hurts cold email so much is covered in your cold email bounce rate is blacklisting your domain.
Keeping it low
Verify lists before sending, keep them tight to a real ICP, warm new domains, and pause a campaign if bounces spike. A few percent is normal; higher rates get the domain throttled or blacklisted, which is why sender reputation and deliverability hinge on it.
Common questions
What is a good email bounce rate?
A few percent is normal for cold outreach; rates climbing past roughly 3 to 5 percent are a warning, and higher gets the domain throttled or blacklisted. Watch the trend and clean the list.
What is the difference between a hard and soft bounce?
A hard bounce is permanent (the address does not exist); a soft bounce is temporary (full mailbox or server down). Hard bounces do the reputation damage.