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How many bounces before a domain is burned?

There's no single magic number, but there is a safe zone. Here's what each sending platform enforces, what mailbox providers actually watch, and the target to aim for.

Updated 2026-10-17

TL;DR

  • Aim for under 2% hard bounces per campaign. Sending platforms and most deliverability teams agree on that.
  • Over 5% is where platforms start pulling the brakes, and where reputation damage builds quickly.
  • New domains are the most fragile. Verify every list before it touches a fresh domain.

What the sending platforms enforce

PlatformBuilt-in bounce brakeDefault
InstantlyPauses the campaign above 5% bounces, after 200 sendsOn
SmartleadPauses at a threshold you choose (bounces ÷ total leads)Off
lemlistAlerts at 10%, pauses at 50% after 100 leadsOn

From each platform's help center, checked 2026-10-17. See our guides to Instantly's auto-pause and Smartlead's bounce protection.

What Google and Microsoft care about

Gmail's bulk-sender rules publish a spam-complaint limit (keep it under 0.3%) but no official bounce number. Mailbox providers still treat repeated sends to addresses that don't exist as a sign of a purchased or scraped list, and it feeds directly into how your domain and IP are rated. Bounces and complaints tend to arrive together: a list that bounces a lot is usually a list that complains a lot.

The practical safe zone

  • Under 2%: healthy. Smartlead reports a median of about 1.5% across its senders.
  • 2-5%: warning. Fix the list before the next send.
  • Over 5%: stop. Your platform probably already has. Verify everything before resuming.

Small samples mislead. One or two bounces on a 30-email day can look like a big percentage. Judge the rate over at least a few hundred sends, and remember a single bad import can push a fresh domain over the edge in a day.

How to stay under 2%

  1. Verify every list before import, including "verified" exports from lead databases. Why Apollo exports still bounce.
  2. Treat catch-alls separately. Should you send to them?
  3. Re-verify lists older than about 30 days, and long sequences before their later steps.
  4. Spread volume across warmed inboxes and domains so one bad batch can't sink everything.
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