Ask around and you will hear very different answers: "under 5% is fine", "anything above 2% is dangerous", "it should be zero". The confusion comes from mixing up lists that were never cleaned with lists that were verified before sending.

This article gives clear numbers, explains where they come from, and shows what to do at each level.

How to calculate your bounce rate

Bounce rate = bounced emails ÷ emails sent × 100.

If you send 500 emails and 12 bounce, your bounce rate is 12 ÷ 500 = 2.4%.

Two details matter:

  • Count hard bounces first. A hard bounce (an address that does not exist, a 5.1.1 error) is the one that hurts your reputation. Soft bounces (a full mailbox, a server that is down) are retried by your sending server and usually resolve on their own. See hard and soft bounces for the difference.
  • Measure each campaign, not your account's lifetime average. One bad list hidden in a good average still does damage on the day you send it.

Bounce rate benchmarks

There is no official bounce limit from Gmail or Outlook. These are the rules of thumb used across the industry, and the ones sending services act on:

Hard bounce rate What it means What to do
Under 1% A list verified shortly before sending Keep doing what you do
1% to 2% Acceptable Look at which part of the list the bounces came from
2% to 5% A warning: many sending services start to warn or pause accounts around 2% Verify the rest of the list before the next send
Over 5% The list was not cleaned, or is old Stop the campaign (see below)

A verified list sent soon after the check, to safe addresses only, normally lands under 1%.

Why new senders need lower numbers

The same 3% bounce rate does more damage to some senders than to others:

  • No history to protect you. A sender with months of opens and replies shows mailbox providers that people want the mail. A new domain or a new sending platform has nothing to balance a bad first impression.
  • Small volumes. If you send 50 emails a day, 3 bounces is already 6%. Each bad address weighs more.
  • Sending services watch closely. Newsletter platforms and email services track bounce rates per campaign and pause accounts that go over their limit, sometimes after a single campaign.

What mailbox providers actually measure

Gmail's sender rules focus on spam complaints (keep them under 0.1%, and never reach 0.3%), on authentication (SPF, DKIM and DMARC) and on whether recipients want your mail. Bounces are not a published rule, but a high bounce rate is one of the clearest signs of a bought or neglected list, and it lowers your reputation along with your complaints and engagement. Our guide to the 2026 sender requirements covers the published rules.

Know your bounce rate before you send

You do not have to find out after the damage is done. When you verify a list with MailQuell, you get a send forecast: the bounce rate to expect if you send now, for the whole list and for its safer parts:

  • Safe only: the lowest bounce rate, best for a new domain or an old list;
  • Safe + role addresses: adds shared inboxes such as info@;
  • Safe + role + catch-all: more contacts, more risk.

Each forecast is shown next to the 2% line, and one click downloads the part we recommend. See how to verify a list in bulk.

How to keep your bounce rate low

  1. Verify every list before the first send, and again if it has not been mailed for a few weeks.
  2. Start with safe addresses on a new domain; add catch-all addresses later, in small batches.
  3. Never buy or scrape lists. They are the main source of high bounce rates and of spam traps.
  4. Check addresses where they enter, on your forms, so typos and fake sign-ups never reach your list (see the email verification API).
  5. Remove every hard bounce right after each send and keep a suppression list.
  6. Ramp up slowly on a new domain or mailbox.

Your bounce rate is over 5%: what to do now

  1. Pause the campaign. Every extra bounce makes the situation worse.
  2. Read the bounce codes. If most are 5.1.1 (no such user), the list is the problem. If most are 5.7.x (policy), the problem is your sending setup or reputation, not the addresses (see why verified emails still bounce).
  3. Verify the addresses that have not been sent yet, and send only to the safe ones.
  4. Check your domain: SPF, DKIM and DMARC, with our SPF and DMARC checker.
  5. Resume slowly, at a lower daily volume, and watch the next sends closely.

Frequently asked questions

Do soft bounces count in the bounce rate?

Most tools show them, but treat them separately. Focus on hard bounces. A soft bounce that repeats on every campaign, though, is usually an abandoned mailbox: remove it after a few attempts.

Is a 0% bounce rate realistic?

On small sends to a freshly verified list, yes. On larger lists, a few bounces are normal: addresses change between the check and the send, and catch-all domains cannot be confirmed in advance.

Does open rate tell me anything about bounces?

No. Open rates are unreliable since some mail apps load images automatically, and they say nothing about addresses that bounced. Track hard bounces, replies and complaints instead.

Check before you send