Soft Bounce vs Hard Bounce
Email MarketingAlso: Email Bounce Types · Bounce Classification
Quick definition
A hard bounce is a permanent delivery failure, usually because the email address doesn't exist. A soft bounce is a temporary failure, usually because the inbox is full or the receiving server is briefly down. Hard bounces should be removed from your list immediately. Soft bounces get a few retries before removal.
How it varies across Australia
Healthy Australian sending lists keep hard bounce rates very low, close to negligible. Soft bounces should also stay low and clear within a few sending cycles. A list where soft bounces persist across multiple sends is usually a data quality problem, not a temporary blip.
See email deliverability benchmarks across Australian industries →What it actually means
Every bounce is a rejection, but not every rejection means the same thing. A hard bounce is the receiving server telling you the address doesn't exist, the domain is dead, or the mailbox has been permanently closed. There's no retry that fixes this. The email address is gone.
A soft bounce is different. The address is real, but delivery failed for now. The inbox is full, the server is temporarily overloaded, or the message was too large. Most email service providers (ESPs) will retry a soft bounce a handful of times over a few days before giving up.
The mistake most senders make is treating bounce rate as one number. It isn't. A spike in hard bounces means your list hygiene has failed, often because of a bad import or stale segmentation. A spike in soft bounces usually points at a deliverability problem, like a receiving domain temporarily throttling your sender IP because your engagement rate dropped.
ISPs (internet service providers) like Gmail and Outlook watch how you handle both. Keep emailing hard-bounced addresses and your sender reputation drops fast. Keep retrying soft bounces past a reasonable point and you look like you're hammering inboxes that don't want you.
A hard bounce is a locked door. A soft bounce is a door that's just busy. Treat them the same and you'll knock down doors that were never going to open.
How it shows up
Hard bounces show up in your ESP's bounce report with codes referencing non-existent addresses, invalid domains, or blocked recipients. Soft bounces show up with codes for full mailboxes, server timeouts, or message size limits. Most ESPs auto-suppress hard-bounced addresses after one attempt and soft-bounced addresses after three to five consecutive failures.
It also shows up in deliverability tools and postmaster dashboards from Gmail and Microsoft, where a rising bounce trend of either type will correlate with dropping inbox placement rates before you notice it in your own open rate.
The Australian context
Australian B2B lists tend to carry higher soft bounce rates than consumer lists because corporate mail servers apply stricter size limits and more aggressive spam filtering. A campaign with large attachments or heavy image weight will soft bounce more often against Australian government and enterprise domains than against typical consumer inboxes.
Under the Spam Act, senders also need a functioning unsubscribe mechanism. A hard bounce doesn't remove your obligation to honour unsubscribe requests from that same contact if they'd previously engaged through another channel, so bounce handling and consent management need to stay linked in your CRM (Customer Relationship Management) records.
Where people get this wrong
Related terms
Common questions
Should I remove an address after one soft bounce?
No. Let your email service provider retry a soft bounce a few times over several days, which is standard practice. Only remove the address if it keeps soft bouncing across multiple consecutive sends, which usually means it should be treated as effectively dead.
Can a soft bounce turn into a hard bounce?
Yes. Most email service providers will reclassify a persistently soft-bouncing address as a hard bounce after a set number of failed attempts, often three to five sends. At that point it gets suppressed the same way a true hard bounce would be.
Does a high soft bounce rate hurt sender reputation?
It can. A rising soft bounce trend often signals that receiving servers are throttling your sender domain due to engagement or authentication issues. ISPs track this pattern over time, so an ignored soft bounce problem can escalate into a broader deliverability issue.
What's the acceptable hard bounce rate for a healthy list?
It should sit close to zero for a well-maintained list. Anything noticeably above that usually points to a stale list, a bad import, or missing email validation at signup, and warrants an immediate hygiene review rather than waiting for the next campaign.
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About New Rebellion
New Rebellion is a marketing intelligence consultancy. We build tools, score Australian businesses on how their marketing actually performs, and publish Debrief every day. This dictionary is part of how we work in the open.
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