What’s the difference between a soft bounce and a hard bounce?
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You send an email. It doesn't get through. But what actually happened? That's where the hard bounce vs soft bounce distinction matters, and it's simpler than it sounds.
The core difference is permanence. A hard bounce means the delivery failed and it won't work next time either. A soft bounce means something temporary got in the way, and the address might accept your email later.
Hard bounces happen when there's no path forward. Common causes include an email address that doesn't exist (the infamous "user unknown" error), a domain with no mail server, or an address that's been deactivated. If you sent to captain@deepcurrent.io and that inbox was deleted last month, you'll get a hard bounce. Remove that address immediately. Continuing to send to it wastes your reputation on a dead end.
Soft bounces are the temporary kind. The mailbox is full, the receiving server is down for maintenance, your message is too large, or the server is rate-limiting you for the moment. Most ESPs will automatically retry soft bounces over the next 24 to 72 hours before giving up.
Here's where it gets a bit messy. Classification isn't always clean. A "mailbox full" bounce could mean your contact is on vacation (genuinely temporary) or that the account has been abandoned for months (effectively permanent). Some ESPs are smart about this and will automatically convert an address from soft to hard after a certain number of consecutive failures. Check your platform's settings so you know where that threshold sits.
As a general benchmark, keep your overall bounce rate under 2%. If you're consistently above that, it usually points to list quality problems worth addressing before they do real damage to your sender reputation. If your hard bounce rate jumps suddenly, that's an emergency, not a slow-burn issue.
If your bounce rates are climbing and you're not sure why, our free Blocklist Checker can rule out domain or IP reputation issues quickly. And if you want a second pair of eyes on your list health, drop us a note and we'll help you figure out what's going on.
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