A bounce happens when your email cannot be delivered and comes back to your email tool, a bit like a letter returned to sender. Every list has a few bounces. Too many is a warning sign to inbox providers that you are not looking after your list.
There are two main types, and they need different handling.
Hard bounces
A hard bounce is a permanent failure. The email will never be delivered to that address. Common reasons:
- The email address does not exist, often because of a typo like gmial.com.
- The domain does not exist or no longer receives email.
- The person left the company, and their work address was closed.
What to do: remove hard bounced addresses straight away. Most email marketing tools do this automatically, marking them as bounced so you never send to them again. Never import hard bounced addresses into another tool.
Soft bounces
A soft bounce is a temporary problem. The address exists, but the email could not be delivered this time. Common reasons:
- The person's inbox is full.
- The receiving server is down or busy.
- The email was too large.
- The receiving server is temporarily limiting how many emails it accepts from you.
What to do: usually nothing at first. Your email tool will often retry for a while. If the same address soft bounces again and again across several sends, treat it like a hard bounce and remove it. Many tools do this automatically after a set number of soft bounces.
What is a healthy bounce rate?
Your bounce rate is the share of emails that bounced. A common rule of thumb is to keep it under 2 percent, and well run lists are often far below that. If your bounce rate suddenly jumps, investigate before your next send.
Why bounces matter
Inbox providers see bounces as a sign of a poorly kept list. Lists full of dead addresses are often old, bought or scraped, which is what spammers do. A high bounce rate can hurt your sending reputation and send more of your emails, even to valid addresses, to spam.
Some old addresses are also turned into spam traps, addresses that exist only to catch senders who do not clean their lists. Removing bounces and inactive contacts keeps you away from them.
How to prevent bounces in the first place
- Use double opt in. New subscribers confirm their email by clicking a link, so typos and fake addresses never join your list.
- Add a typo check to your signup form. Some forms suggest corrections, like "Did you mean gmail.com?"
- Send regularly. Lists that go quiet for a year come back with many dead addresses.
- Clean your list every few months. Remove contacts who have not opened or clicked in a long time after trying to win them back.
- Verify old lists before importing. If you have an old list, an email verification service can flag invalid addresses before you send.
When bounces spike
If a send suddenly bounces much more than usual:
- Check the bounce messages in your email tool. They often explain the reason.
- Look for a pattern. If most bounces come from one provider, that provider may be blocking you, which is a reputation problem rather than a list problem.
- Pause big sends until you understand the cause.
The short version
Hard bounces are permanent. Remove them immediately. Soft bounces are temporary. Watch them and remove repeat offenders. Keep your overall bounce rate low with double opt in, regular sending and regular list cleaning.
Mailbox providers update their filters and requirements regularly. This guide was last reviewed on May 17, 2022. Spotted something out of date? Tell us.