What is a good email bounce rate? (And the number that gets you throttled)

If you send email to a list, your bounce rate is the single number mailbox providers watch most closely. It's also the one most senders never look at until something breaks.

This guide covers what counts as a bounce, what a "good" rate actually is, and where the throttling thresholds sit.

Hard bounces vs. soft bounces

A hard bounce is permanent. The address doesn't exist, the domain has no mail server, or the mailbox was deleted. Sending to it again will never work.

A soft bounce is temporary. The inbox is full, the server is busy, or your message was too large. The address is real, it just couldn't be delivered right now.

Mailbox providers care about both, but hard bounces are the ones that damage your reputation. Sending to addresses that don't exist is the clearest possible signal that you didn't get those addresses from real people.

What counts as a good bounce rate

Here's the honest version of the numbers:

• Under 2% is where you want to live. This is what a well-maintained list looks like.
• 2 to 5% is a warning. You're not in trouble yet, but your list has rot in it and it's getting worse.
• Over 5% is where mailbox providers start to act. Gmail's Postmaster guidelines flag spam rates above 0.3% and treat sustained bounce rates in this range as a sign of poor list acquisition.
• Over 10% and most email platforms (Mailchimp, Klaviyo, Kit and the rest) will pause your account or force you through a list review before you can send again.

In practice the throttling starts earlier than the public thresholds. Providers don't publish the exact numbers, but senders consistently report slower delivery and more messages landing in spam once hard bounces cross the 3% mark.

Why lists go bad

Even a list built entirely from real opt-ins decays. Estimates vary, but somewhere between 20% and 30% of a B2B list stops working every year. People change jobs, companies rebrand their domains, and personal addresses get abandoned.

The other big source of bounces is the sign-up form itself. Typos (gmial.com, hotmal.com), fake addresses entered to get past a gate, and disposable addresses from services like Mailinator all end up on your list looking perfectly normal until you send to them.

How to bring the rate down

Clean before you send, not after. Verifying a list takes minutes. Rebuilding a sender reputation takes weeks.

Remove hard bounces immediately. Any address that hard-bounced once should never receive email from you again. Most platforms do this automatically; check that yours does.

Treat old segments with suspicion. If a segment hasn't been emailed in six months or more, verify it before you re-engage. This is the single most common way senders blow up an otherwise healthy domain.

Watch the role and catch-all addresses. info@, sales@ and similar inboxes rarely bounce, but they're rarely read by the person you're trying to reach either, and they generate a disproportionate share of spam complaints.

Where a verification tool fits

A verifier checks each address against the actual mail server before you send. It confirms the domain accepts mail, tests whether the specific mailbox exists, and flags disposable, role and catch-all addresses so you can decide what to do with them.

For a list under a few thousand addresses, a one-off clean before a campaign is usually enough. For larger or older lists, cleaning every quarter keeps you comfortably under the 2% line.

ListBouncer runs exactly this kind of check. Upload a CSV, and you get back the same list split into valid, risky, and bounce-likely buckets, with the addresses that will bounce already separated out.