Why did my campaign pause for bounces?

Short answer: too many of the emails that campaign sent came back undeliverable, so WarmySender stopped it. A high bounce rate is the single fastest way to lose your place in the inbox — not just for that campaign, but for every campaign you send from the same addresses — so we stop the campaign before the damage is done rather than after. Nothing is broken, nothing is lost, and none of your other campaigns are affected. The fix is to clean the contact list, then start the campaign again yourself. That last part is deliberate: we do not restart it for you, because the thing that causes bounces is the list, and restarting on its own would just send more email to the same bad addresses.

WarmySender runs your outreach on autopilot with AI agents, across Cold Email, Email Warmup, LinkedIn, Instagram and Multichannel sequences — plus real-time email verification. This page covers a Cold Email protection that is always running, on every campaign.

How do I know this is what happened?

You will see both of these on the campaign, and they describe the same thing:

• A status badge reading Cooldown.
• An amber notice reading “Paused — high bounce rate”, with the line: “Too many of your emails bounced, which can hurt your sender reputation. Clean or re-verify your contact list, then click Resume to continue.”

You will also have an email about it. When bounces pause a campaign we email the workspace owner straight away, naming the campaign, the bounce rate it reached and the limit it crossed, so nobody discovers a stopped campaign three days later. (You can switch that email off under Settings → Bounce Shield if you would rather not receive it — the pause itself still happens either way.)

If your campaign is stopped but you see a different message, this is not your page — jump to what else can stop a campaign below.

What exactly triggers the pause?

Two conditions have to be true at the same time.

1. The campaign has sent at least 50 emails. Below that, nothing can trip. This floor exists so a couple of unlucky bounces early on cannot stop a campaign that is perfectly healthy — on a list of 20, two dead addresses is 10%, and that number means nothing yet.
2. Its bounce rate is above its limit. The built-in limit is 5%. Exactly 5.0% does not trip it; above 5% does.

The bounce rate is simply the share of that campaign’s sends that came back undeliverable — bounces divided by emails sent, written as a percentage. It counts that one campaign only. A different campaign with a clean list carries on sending normally the whole time.

A worked example

Say a campaign has sent 400 emails and 26 of them bounced.

• 26 ÷ 400 = 0.065, which is 6.5%.
• 400 is comfortably over the 50-send floor, so the check is live.
• 6.5% is above the 5% limit, so the campaign stops.

Now the same list earlier in its life: 40 sent, 4 bounced. That is 10% — twice the limit — and nothing happens, because 40 is below the 50-send floor. The list is just as bad; we simply do not have enough sends yet to say so fairly. Ten more sends later, the check goes live and the campaign stops.

This is worth knowing because it explains something that otherwise looks arbitrary: a campaign can run for a while, look fine, and then stop — not because anything changed, but because it finally sent enough email to be judged.

What is a normal bounce rate?

Under 3% is the number to aim for, and a well-maintained list usually sits under 2%. Between 3% and 5% is worth a look but will not stop anything. Above 5% is the range where mailbox providers start reading your sending as “this sender is working from an out-of-date list”, and that judgement follows your sending addresses around — it is not confined to the campaign that caused it. That is the whole reason the limit sits where it does.

Almost every high bounce rate has the same cause, and it is not a mistake you made: lists go stale on their own. People change jobs, companies close mailboxes, addresses get retired. An export that was accurate a year ago can easily be 10% dead today without anyone doing anything wrong.

Why don’t you just resume it for me?

Because restarting is not the fix, and doing it automatically would quietly make things worse.

A high bounce rate is not a hiccup that passes with time, like a busy mail server or a temporary rate limit. It is a statement about the contact list: a measurable share of those addresses no longer exist. Nothing about waiting changes that. If we restarted the campaign on a timer, it would send more email to the same list, bounce at the same rate, stop again, and each round would take a little more of your sender reputation with it — while looking, from the outside, like the system was busy handling it.

So the pause holds until a person decides it is ready. The one action that actually fixes a bounce rate is a cleaner list, and that is a decision only you can make. Once you have made it, resuming takes one click.

How do I clean the list before I resume?

Work through these in order. The first two do most of the work.

1. Look at which addresses actually bounced. Open Inbox → Campaigns tab → Delivery Issues for the list of recipients whose email did not land, with a plain-language reason for each. Read the pattern before you act on it: bounces clustered on a single company domain usually mean one stale export or one company that changed its mail setup, not a bad list overall. Bounces scattered evenly across many domains mean the list itself is old. Full walkthrough: How to see emails that didn’t get delivered.
2. Run the remaining contacts through email verification. This is the step that genuinely fixes the number, and it is built into WarmySender — open the Email Verifier, upload or select the list, and it tells you which addresses are still real before you spend another send on them. Remove everything that comes back Invalid. Addresses marked Risky are usually a catch-all setup on the receiving end rather than a fault in your list; they are normally fine to keep, especially with warmup running. What each result means: What email verification results mean.
3. Put the cleaned list back on the campaign. Verifying builds a cleaned list for you automatically, and applying it to a running campaign never re-sends to anybody who has already been emailed. The exact steps: Apply a verified list to a campaign without duplicates.
4. Check where the list came from. If it was bought, scraped, or exported from a system more than a few months ago, expect it to keep degrading, and verify it as a habit before each campaign rather than after a pause. Fresh contacts from the built-in Leads database avoid this entirely.
5. Leave warmup running. It does not lower your bounce rate — nothing but a better list does that — but it is what rebuilds the sender reputation the bounces cost you. See How warmup protects your deliverability.

You do not have to remove the bounced addresses yourself. Every address that bounces for good is added to your Blocklist automatically the moment it happens, and none of your campaigns will try it a second time — not the rest of this one, and not a campaign you build next month.

How do I start it again — and will it just stop straight away?

Open the campaign and click Resume. It starts sending again on its normal schedule.

It will not immediately stop again, and this is the part worth understanding, because the arithmetic looks alarming until you know what we do about it. When you resume, we take a fresh baseline and measure the bounce rate only on what the campaign sends from that moment on. The bounces that caused the pause are not held against the cleaned list.

The same worked example, continued

The campaign paused at 400 sent and 26 bounced (6.5%). You verify the list, drop the dead addresses, and resume. Over the next 200 sends, 4 bounce.

• Measured from the resume: 4 ÷ 200 = 2%. Comfortably under the limit, so the campaign keeps running.
• Measured on the old running totals it would have been 30 ÷ 600 = 5% — dragging the pause behind it and leaving you one bounce away from stopping again through no fault of the new list.

The fresh baseline is what makes cleaning the list worth doing. Your campaign is judged on the list you fixed, not the one you replaced.

One thing to get right: clean the list first, then resume. Resuming without changing anything will send into the same addresses, bounce at the same rate, and stop again after another 50 sends — and those 50 sends are spent from your sending reputation.

Can I make it stop even earlier than 5%?

Yes, and there are two places to do it.

• Across the whole workspace — go to Settings → Bounce Shield, turn on “Use my own, stricter limit”, and set the number you want. It applies to every campaign in the workspace, including ones you already built.
• On one campaign — the campaign editor has a Bounce Rate Threshold under its advanced sending settings, for when one campaign needs different treatment from the rest.

Where both exist, we always use whichever is lower. That is the one rule to remember, and it only ever runs in your favour: this setting can tighten protection and is arithmetically incapable of loosening it. Setting the workspace number higher than a campaign’s own limit changes nothing at all — the campaign keeps the stricter one.

What a stricter limit does, in numbers

Take the same campaign, and set the workspace limit to 3%. Its own limit is the built-in 5%; the lower of the two wins, so 3% is what applies. At 400 sent it now stops on the 13th bounce — 13 ÷ 400 = 3.25%, which is above 3% — where under the built-in limit it would have carried on to the 21st (21 ÷ 400 = 5.25%). Eight fewer dead addresses reached before anyone noticed. That is the whole trade a stricter limit buys: you stop sooner, on less evidence, and accept the occasional early stop on a list that was actually fine.

A good rule: if you send to lists you did not build yourself, set it to 3%. If your lists are verified before every campaign, the built-in 5% is already generous and there is nothing to change.

Can I switch bounce protection off?

No, and that is deliberate rather than an option we forgot. Two things are always running on every campaign, in every workspace:

• Campaigns pause themselves on high bounces.
• Addresses that bounce for good are never emailed again — they go on your Blocklist automatically, so no campaign can try them a second time.

These are not switches with a sensible “off”. The damage a bad list does is not confined to the campaign that sent it: it attaches to your sending addresses and your domain, and it takes far longer to rebuild than it took to lose. Turning the guard off would only ever mean finding out later, from a drop in replies across everything you send. In Settings → Bounce Shield these are shown as always-on protections rather than as switches, for exactly that reason.

What you can change is where the line sits, in the direction of more protection, and whether we email you when it fires.

What does not pause a campaign — and what else can

Two things people expect to stop a campaign, which do not:

• Unsubscribes never pause a campaign. Somebody opting out cleanly is a healthy outcome in cold email — it is the alternative to being reported — so it is not treated as a fault. They are removed from your campaigns immediately and added to your suppression list, and the campaign carries on. See the unsubscribe link in campaign emails.
• Spam complaints never pause a campaign — because we genuinely cannot see them, and it is better you know that than wait for a warning that will never arrive. Your campaigns send from your own connected mailbox, so when a recipient reports a message, that report goes to their mailbox provider and no copy reaches WarmySender. Track your complaint rate where it is actually reported: Google Postmaster Tools for Gmail, Microsoft SNDS for Outlook, aiming under 0.1%.

And the other reasons a campaign can stop, so you can tell them apart at a glance:

The distinction that matters: the first three are safety pauses and wait for a person, because something needs changing before more email goes out. The last two clear themselves and need nothing from you.

Frequently asked questions

Why did my campaign stop by itself?

Too many of its emails came back undeliverable. Once a campaign has sent at least 50 emails, if more than 5% of them bounce, WarmySender stops it to protect your sender reputation. You will see a Cooldown badge and a notice reading “Paused — high bounce rate”, and the workspace owner gets an email naming the campaign and the number it reached. Nothing is lost and your other campaigns keep sending normally — only this campaign is affected, and only until you clean its list and start it again.

How is the bounce rate worked out?

It is the share of that campaign’s sends that came back undeliverable: bounces divided by emails sent, as a percentage. So 26 bounces out of 400 sends is 6.5%. It only ever counts the one campaign, never your account as a whole. Two conditions must both be true for it to stop anything: at least 50 emails sent, and a rate above the limit. Exactly 5.0% does not trip it; above 5% does.

Why did a campaign with a terrible bounce rate keep running?

Because it had not sent 50 emails yet. Below that floor the check does not run at all, and it is there on purpose: on a list of 20, two dead addresses is 10%, which tells you nothing. The list is not being judged as fine — there is simply not enough sending to judge it on. Once it passes 50 sends the check goes live, which is why a campaign can run for a while, look healthy, and then stop without anything having changed.

Will it start again on its own if I wait?

No, and waiting will not help. A high bounce rate is not a temporary condition that passes — it is a statement about the contact list, and time does not change how many of those addresses exist. If we restarted the campaign automatically it would send into the same list, bounce at the same rate, stop again, and cost you a little more sender reputation each round. The pause holds until you have cleaned the list and clicked Resume yourself.

What do I actually do to fix it?

Look at which addresses bounced under Inbox → Campaigns tab → Delivery Issues, then run the remaining contacts through the built-in Email Verifier and drop everything that comes back Invalid. Apply the cleaned list back to the campaign — that never re-sends to anyone already emailed — and click Resume. You do not need to remove the bounced addresses yourself; they were added to your Blocklist automatically the moment they bounced.

If I resume, will it just stop again straight away?

Not if you cleaned the list. When you resume we take a fresh baseline and measure the bounce rate only on what the campaign sends from that point on, so the bounces that caused the pause are not held against the new list. A campaign that paused at 400 sent and 26 bounced, then sends 200 more with 4 bounces, is measured at 4 divided by 200 = 2% and keeps running — not at 30 divided by 600 = 5%. Resuming without changing anything, though, will stop again after about another 50 sends.

Do I have to remove the bounced addresses myself?

No. Every address that bounces for good is added to your Blocklist automatically the moment it happens, and the contact is marked as bounced. None of your campaigns will email it again — not the rest of the campaign it bounced on, and not a campaign you build later. That happens on every workspace and cannot be switched off, because re-mailing an address that has already bounced is one of the fastest ways to damage a sending domain.

Can I make campaigns stop at a lower bounce rate?

Yes. In Settings → Bounce Shield, turn on “Use my own, stricter limit” and set your number — it applies to every campaign in the workspace. An individual 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 setting can only ever tighten protection; setting it higher than a campaign’s own limit changes nothing. A good rule: 3% if you send to lists you did not build yourself, and leave the built-in 5% alone if you verify before every campaign.

Can I turn bounce protection off completely?

No. Pausing on high bounces and blocking addresses that have bounced both run on every campaign in every workspace and have no off switch. That is deliberate: the harm from a bad list attaches to your sending addresses and your domain rather than to one campaign, and it takes much longer to rebuild than to lose. What you can change is where the line sits — in the stricter direction — and whether we email you when it fires.

Do unsubscribes or spam complaints pause my campaign?

Neither. Unsubscribes are a healthy outcome in cold email — someone opting out cleanly is the alternative to being reported — so they never stop a campaign; the person is removed from your campaigns and added to your suppression list, and sending carries on. Spam complaints never pause a campaign either, because we cannot see them: your campaigns send from your own mailbox, so a report goes to that recipient’s mailbox provider and no copy reaches us. Watch your complaint rate in Google Postmaster Tools or Microsoft SNDS instead, aiming under 0.1%.

Does this affect my other campaigns or my mailboxes?

No. The bounce rate is measured per campaign, so only the campaign that crossed its limit stops. Your other campaigns keep sending on their normal schedules, your mailboxes stay connected, and warmup carries on as usual. The one thing that does reach across is the Blocklist: an address that bounced anywhere will not be emailed by any of your campaigns, which is protection rather than a side effect.

I verified the list and it still bounced. Why?

Verification is a snapshot of the moment it ran, not a permanent guarantee — a mailbox that existed last week can be closed today, especially when someone leaves a company. A small residue of bounces on a verified list is normal and well under the limit. If a verified list bounces heavily, the usual explanations are a long gap between verifying and sending, or a list made largely of catch-all domains, where no verification service can confirm an individual mailbox. Verify close to when you send, and the number stays low.

Related pages

• How to see emails that didn’t get delivered — the list of recipients whose email did not land, and what each reason means. Start here when a campaign pauses.
• What email verification results mean — Valid, Invalid, Risky and Unknown, and which ones to remove before you resume.
• Apply a verified list to a campaign without duplicates — putting the cleaned list back without re-emailing anyone.
• Why a prospect was marked as bounced — the same protection at the level of one contact rather than a whole campaign.
• How my campaign metrics are calculated — where the bounce rate on your campaign card comes from.
• Why is my campaign paused after a payment issue? — the other “my campaign paused” page, and the one that clears itself.
• How warmup protects your deliverability — rebuilding sender reputation after a rough patch.