How should I handle hard bounces?
Still have a question, spotted an error, or have a better explanation or a source we should cite?
A hard bounce is a permanent delivery failure. The receiving server is telling you clearly: this address doesn't exist, the domain doesn't accept mail, or the mailbox is permanently disabled. There's no retry that changes that answer.
The rule is simple: remove hard bounces immediately after the first failure. Don't wait for a pattern. Don't send a second time to confirm. A single hard bounce is definitive.
Most ESPs handle this automatically. When an address hard bounces, the platform will suppress it from future sends. But "automatic suppression" and "removed from your list" aren't always the same thing. Some ESPs suppress without cleaning the contact record. That means the contact still counts toward your billing tier even though you can never email them. Worth checking your specific platform's behavior and cleaning the hard-bounced records out entirely if you're paying per contact.
Common reasons you'll see hard bounces:
- The address never existed (typo at signup, fake signup)
- The mailbox was deleted (person left the company, closed their account)
- The domain expired or shut down
- The address was disabled by the provider (policy violation, inactivity)
If your hard bounce rate exceeds 2% on a send, that's a signal worth taking seriously. It means a meaningful chunk of your list is either stale or was never valid to begin with. The fix is validation before the next large send, and a look at your acquisition process to understand where these addresses came from.
If you're over 2% and not sure why, we're happy to take a look. Our list cleaning service will also catch most hard-bounce candidates before you send, which is a lot gentler on your reputation than finding out the hard way.
Contributors
Who worked on this answer
Every name links to their profile. Every company links to their site. Real people, real accountability.
