Bounce Shield Protection
A bad list is the fastest way to damage a sending domain, so WarmySender guards against it in two ways. Both are on by default and neither needs configuring.
1) Every bounced address is suppressed automatically
The moment an address hard-bounces it goes on your suppression list and the contact is marked bounced. Nothing sends to it again — not the rest of that campaign, and not a later one. You never have to clean it out by hand.
2) A campaign that bounces too much stops itself
Every campaign carries its own bounce-rate threshold, 5% by default — and 5% is also the most a campaign can be set to. Once a campaign has sent at least 50 emails, if its bounce rate is above that threshold the campaign stops and the campaign card shows you why. The 50-send minimum is there so two unlucky bounces on a small campaign can't trip it.
A campaign stopped this way stays stopped until you resume it. That is deliberate — what fixes bounces is a cleaner list, and resuming on its own would just send more of the same. When you do resume, the bounce measurement starts fresh from that moment, so the earlier bounces don't immediately stop it again.
3) You can make it stricter, never looser
Settings → Bounce Shield → 'Use my own, stricter limit' sets a lower number for every campaign in the workspace. A single campaign can also carry its own limit in the campaign editor's advanced sending settings. Where both exist we always use whichever is lower, so this can only ever tighten protection — setting it above a campaign's own limit changes nothing at all. 3% is a sensible choice if you send to lists you didn't build yourself.
Why you can't go above 5%: 5% is the most we allow, to protect your sending domains. It is the industry ceiling for cold email (the usual guidance is under 5%, ideally 2% or lower), and past it mailbox providers start treating you as a sender with an out-of-date list. Example: after 1,000 sends a 5% limit has stopped the campaign by its 51st bounce; a 10% limit would have let it reach 100. If you type a higher number in the campaign editor it is set to 5% and the field tells you why; the API and AI agents get the same answer and the higher number is not saved.
You'll know when it fires: the workspace owner gets an email naming the campaign, the bounce rate it reached and the limit it crossed, so a stopped campaign is never a silent one. That email can be switched off in the same place; the pause itself always happens.
What to do when a campaign stops for bounces:
- Verify the list before you resume — that is what actually fixes it, and email verification is built into WarmySender.
- Look at which addresses bounced. A cluster on one domain usually means a stale export rather than a bad list.
- Then resume the campaign from the campaign page.
Best practice: verify every list before you import it. A verified list is the difference between a campaign that runs and one that keeps stopping.
Full walkthrough — what the number means, the arithmetic worked through, the list-cleaning steps, and why resuming is deliberately a manual step: warmysender.com/documentation/why-did-my-campaign-pause-for-bounces