Two types of email delivery failure, one permanent, one temporary, and knowing the difference changes what you should do next.
What Is a Hard Bounce?
A hard bounce means an email cannot be delivered for a permanent reason, usually because the address doesn’t exist, the domain is invalid, or the recipient’s server has blocked delivery entirely. Sending to it again will not fix anything.
What Is a Soft Bounce?
A soft bounce is a temporary failure. The address is valid, but something short-term is blocking delivery, a full mailbox, a server that’s temporarily down, or a message that’s too large. Sending again later usually works fine.
Why the Difference Matters
Hard Bounce vs Soft Bounce, Compared
| Fields | Hard Bounce | Soft Bounce |
|---|---|---|
|
Cause
|
Invalid address, blocked domain
|
Full mailbox, temporary server issue
|
|
Fix
|
Remove from list immediately
|
Retry later, monitor if repeated
|
|
Reputation impact
|
Direct, should never repeat
|
Minimal if occasional
|
|
Common ecommerce example
|
Customer typo at checkout
|
Vacation auto-responder full mailbox
|
How to Handle Each One
1. Hard bounces: Remove from your list immediately, do not retry
2. Soft bounces: Allow automatic retries, but if the same address soft bounces repeatedly across several sends, treat it like a hard bounce and remove it
3. Review bounce trends after every campaign, not just occasionally
How Adflipr Helps
Best Practices
– Remove hard bounces the moment they happen, don’t wait for a monthly cleanup
– Watch for addresses that soft bounce three or more times in a row, and treat them as hard bounces
– Keep your overall bounce rate under 2%, higher than that signals a list quality problem
– Use email validation at signup to catch typos before they ever become a bounce
Common Mistakes
– Letting hard bounces sit in the list for months, which slowly damages sender reputation
– Treating every soft bounce as harmless without checking for repeat patterns
– Not validating emails at checkout or signup, letting typos into the list in the first place
– Ignoring bounce data until a big campaign underperforms
Frequently Asked Questions
Yes, right away. There’s no scenario where retrying a hard bounce works, and leaving them in your list only hurts your sender reputation with every future send.
Common causes are a full mailbox or a temporarily unavailable server. Most resolve on their own within a few retries. If the same address keeps soft bouncing across multiple campaigns, it’s worth treating like a hard bounce.
Above 2% is generally considered a warning sign. Consistently high bounce rates suggest your list has quality issues, which inboxes factor into how much they trust your domain.
Yes, directly. Bounce rate is one of the clearest signals inboxes use to judge whether you’re managing your list responsibly, and a high rate can affect deliverability across your entire sending domain, not just the campaign that caused it.
