What Is a Good Email Bounce Rate (and How to Lower It)

No mailbox provider publishes an official bounce limit, but a common rule of thumb in cold outreach is to keep hard bounces under 2% of the emails you send, and a list verified right before sending should come in well below that. If a campaign goes over, pause it and clean the list before sending more. Google, Yahoo and Microsoft all tell senders to drop addresses that bounce, and repeated sends to dead addresses wear down your sender reputation.

How to calculate your bounce rate

Bounce rate is the share of the emails you sent that came back undelivered:

Bounce rate = bounced emails ÷ emails sent × 100

For example, you send 800 emails in a campaign. Twelve come back because the mailbox doesn't exist (hard bounces) and six because the mailbox is full (soft bounces). Your hard bounce rate is 12 ÷ 800 = 1.5%, and your total bounce rate is 18 ÷ 800 = 2.25%.

Three habits make the number useful:

• Track hard and soft bounces separately. They mean different things and need different fixes.
• Track by list source and by sending mailbox, not only by campaign, so you can see which list or which mailbox causes the trouble.
• Count late bounces. Some servers accept a message and send the bounce minutes or hours later, so a campaign's bounce rate can keep rising after the send.

Sending tools don't all count the same way (some divide by delivered emails instead of sent ones), so compare numbers from the same tool.

What is a good email bounce rate?

Google and Yahoo publish a hard number for spam complaints (0.3%), but none of the big providers' sender guidelines puts a number on bounces. The benchmarks senders use are rules of thumb, and for cold outreach they look like this:

Soft bounces move around more and mostly clear on retry. What matters is whether the same addresses keep failing, and whether you see rate-limit deferrals, which warn about your reputation rather than your list.

Your sending platform may also enforce its own limits. Many email service providers publish bounce thresholds in their terms and pause accounts that exceed them, so check yours.

Why B2B lists bounce

Business addresses stop working for ordinary reasons:

• People leave. When an employee leaves, their mailbox is usually closed. A list of named contacts starts decaying the day it's compiled.
• Companies close, merge or rebrand. The old domain stops taking mail or lapses entirely.
• Addresses were guessed. A firstname.lastname@ address built from a pattern may never have existed.
• Typos and formatting errors. A missing letter, .con instead of .com, a stray space from a spreadsheet.
• Mailboxes go dormant. An info@ address nobody checks fills up and starts refusing mail.
• Catch-all domains reject later. They accept every address during delivery, then bounce the ones that don't exist. Our guide to catch-all emails explains how to handle them.
• Your mail is refused. Authentication failures, blocklists and reputation problems cause bounces that have nothing to do with the address. The next section shows how to tell them apart.

A verification check shortly before sending catches addresses and domains that don't exist and addresses that are malformed, and it flags catch-all domains so you can decide what to do with them. Refusals are about your setup, not your list. That's why the most effective fix is to verify the list right before you send, then send soon after: a mailbox that exists today can close next month. Our guide to verifying an email address without sending explains how the check works, and building the list from a live source, such as businesses on Google Maps found the day you search, keeps old data out from the start.

Hard bounces vs soft bounces

A bounce is a delivery failure reported back to you, either during the delivery itself or afterward, as a message from "Mail Delivery Subsystem", "MAILER-DAEMON" or "postmaster" with a subject like "Undeliverable" or "Delivery Status Notification (Failure)". The codes inside tell you what kind of failure it was. In SMTP, a reply that starts with 5 is a permanent failure, and the sending server "SHOULD NOT repeat the exact request"; a reply that starts with 4 is transient, and "the action may be requested again" (RFC 5321, section 4.2.1). The enhanced status code that follows, like 5.1.1, says why (RFC 3463).

• Hard bounce: permanent. The mailbox or the whole domain doesn't exist. Remove the address and never send to it again.
• Soft bounce: temporary. The mailbox is full, the server is busy or it's slowing you down. Your mail server usually retries on its own; if the same address keeps failing, stop sending to it.
• Block bounce: a refusal aimed at you, not at the address: failed authentication, a blocklist or a reputation problem. Removing the address doesn't help; fixing your setup does.

These are bounce messages you'll actually see, with what to do about each:

The message texts come from Gmail's list of SMTP errors and codes and Microsoft's page on Directory-Based Edge Blocking, the setting that makes Microsoft 365 reject unknown recipients.

Why bounces hurt your sender reputation

Providers treat bounces as a sign of list quality. Google's sender guidelines tell senders to "automatically unsubscribe recipients who have multiple bounced messages" and, when messages start bouncing or being deferred, to "reduce the sending volume until the SMTP error rate decreases". Yahoo asks senders to "remove invalid recipients from your list promptly" (Yahoo's sender best practices), and Microsoft lists bounce management among its recommendations for senders. A sender who keeps mailing dead addresses looks like one who doesn't know where the list came from.

Dead addresses can turn into spam traps. Spamhaus describes "dead" traps as once-valid addresses that reject mail with a hard bounce "for a period of time, often 12 months or more" and are then "silently turned back on in the form of spamtraps". Trap operators also buy expired domains and collect the mail that still arrives (Spamhaus). Keep mailing an address that bounced, and one day you may be mailing a trap. That's why suppression has to be permanent.

Filters slow you down, then stop you. Providers can respond with temporary rate limits, like Gmail's 421 4.7.28 deferral, and then with outright rejections. By that point your valid addresses suffer too.

Cold outreach has the least slack. There is no history of wanted mail from you to balance out a bad list, so the list has to be clean from the first send.

How to lower your bounce rate: a checklist

1. Verify every list right before a campaign, not when you collected it.
2. Send soon after verifying. Mailboxes close all the time; a common rule of thumb is to re-verify any list that has sat unused for more than a month.
3. Send only to valid addresses in your main campaign. Decide about catch-all and unknown addresses separately, if at all.
4. Never send to guessed addresses without verifying them first.
5. Suppress hard bounces at once and for good, across every mailbox, domain and tool you send from.
6. Suppress repeat soft bounces. A common rule of thumb is to stop after three soft bounces in a row to the same address.
7. Drop whole domains that don't accept mail, not just the one address that bounced.
8. Clean the formatting before verifying: trim spaces, remove duplicates and fix obvious typos like gmial.com.
9. Authenticate your domain with SPF, DKIM and DMARC so block bounces don't pile up. Our cold email deliverability rules cover the setup.
10. Ramp up volume slowly on new domains and mailboxes, and slow down as soon as bounces or deferrals rise.
11. Compare list sources. If one source produces most of your bounces, stop using it.

What to do when your bounce rate spikes

1. Pause the campaign, or the mailbox it's sending from.
2. Export the bounces and read the codes. Group them into address problems (5.1.x, 5.2.2) and sender problems (5.7.x, 4.7.x).
3. For address problems, suppress every bounced address, find where they came from (an old list, a guessed segment, catch-alls) and re-verify the rest of that source before sending again.
4. For sender problems, check that SPF, DKIM and DMARC pass, look up your domain on the major blocklists and cut your daily volume.
5. Resume at a lower volume and increase slowly, as Google's guidelines advise, watching the bounces of each new batch.

FAQ

Is a 5% bounce rate bad?

For cold outreach, yes. At 5%, one email in twenty goes to an address that doesn't work, well above the common 2% rule of thumb. It usually means the list is old or wasn't verified. Stop and clean it before sending more.

Do soft bounces hurt sender reputation?

Occasional soft bounces are normal and mostly clear on retry. Repeated soft bounces to the same address mean the mailbox is effectively dead, and a wave of rate-limit deferrals means a provider is slowing you down. Treat both as warnings.

Does email verification guarantee zero bounces?

No. Verification catches addresses that don't exist at the time of the check. It can't confirm addresses on catch-all domains, and a mailbox can close between the check and your send. Verify close to sending and expect a small remainder.

Should I remove role addresses like info@ to lower bounces?

Not when you sell to local businesses. A role address published on the business's own website is often the address the owner reads. Verify it like any other address and keep it if it passes.

Is email bounce rate the same as website bounce rate?

No. Website bounce rate, in analytics tools, describes visits that leave without engaging. Email bounce rate is the share of messages that couldn't be delivered.