THIS ARTICLE IS FOR: All ListKit customers
Stage: Live / Troubleshooting
Owner: CS
Last updated: Aug 2026
TL;DR
If your bounce rate hits 5% or more, follow the 5-step protocol below
There are two causes, Google blocking your emails due to sending patterns, or invalid lead addresses, and this protocol fixes both at once
Pause your campaigns, add spintax, remove all links, reverify your leads, then restart ramp-up
Do not skip the ramp-up restart and jump straight back to full volume, that is what caused the spike in the first place
Watch the full walkthrough
Our team recorded a full video walking through this exact protocol, showing each step live inside ListKit. Watch it here if you prefer to follow along visually:
Understanding bounce rates
A bounce happens when an email you send fails to reach the recipient. This is completely normal in cold email, every sender experiences bounces, and it does not mean something is broken. What matters is keeping your bounce rate under control.
There are two types of bounces you might see.
Sender bounce. This happens when your inbox provider, Google, in ListKit's case, blocks the email before it even leaves your inbox. Google does this when it detects a pattern in your sending behavior, usually because the same email copy is going to too many people without variation, or because your inboxes are sending at too high a volume too quickly. This has nothing to do with your leads, they are still valid. It is a sending behavior issue and it is fully fixable.
Hard bounce. This happens when the lead's email address is invalid, the address does not exist or has changed since it was verified. Even with triple verification, email addresses can become invalid quickly because people change jobs, companies shut down, and inboxes get deleted. This is why re-verifying your leads periodically is good practice.
Both types of bounces are a normal part of cold email. The goal is not zero bounces, it is keeping your bounce rate under 5% and fixing it quickly when it spikes. The protocol below covers both types at once, so you do not need to diagnose which one you have before taking action.
The 5-step protocol
If your bounce rate hits 5% or more, follow these five steps in order.
Step 1: Pause your campaigns
Pause all active campaigns for 48 hours. Go to Campaigns, click the three dots next to your campaign, and hit Pause. Do not send anything for two full days.
Step 2: Add spintax to your copy
Spintax sends variations of your email so Google does not see the exact same message going out to thousands of people. It looks like this:
{Hello|Hi|Hey} {{first_name}}
The system randomly picks one option per send. Do this for your entire script, subject line, body, and signature, not just the greeting.
The easiest way to do this at scale is to copy your full script, paste it into Claude or ChatGPT, and ask it to spintax the whole thing for you.
For the full breakdown on syntax and best practices, see: How do I use Spintax in ListKit?
Step 3: Remove all links
No links anywhere in your email. Not in the body, not in the signature.
Go to Inboxes, click Select All at the top, click Update Signature, remove any links from the signature, and save.
Double check your email body as well, some people accidentally leave a link in their signature or copy without realizing it.
Step 4: Reverify your leads
Go to Order History and download your leads as a CSV.
Go to the Email Verification tab under People. Upload the CSV and run verification. This takes 10 to 15 minutes.
Once verification is complete, download only the valid leads. Remove anything marked risky or invalid.
Go back to your campaign, click Upload CSV, and upload the cleaned list.
Step 5: Restart your ramp-up
After the 48-hour pause and once the previous steps are complete, go to your campaign, click Select All on your inboxes, and click Restart Ramp-Up. Confirm by clicking I understand my sending limits.
This resets sending to 1 email per day per inbox, automatically adding 4 emails per day until reaching the full limit of 25 emails per day, the same ramp-up schedule used when your inboxes are first set up.
Do not skip this step and jump straight back to full volume. Sending at full volume immediately after a bounce spike is what caused the issue in the first place, the ramp-up gives your inboxes time to rebuild trust with Google gradually.
Expected outcome
Following all five steps addresses both possible causes of a bounce spike at the same time, sending pattern issues and invalid leads. Once your ramp-up completes again, your bounce rate should return to a healthy range under 5%.
Frequently asked questions
How do I check my bounce rate?
Go to Campaigns and check the bounce rate on your active campaign. If it is 5% or higher, follow the protocol above.
Do I need to do all 5 steps, or can I skip some?
Do all five. The protocol is designed to fix both possible causes of a bounce spike at once, skipping steps means you may only be addressing half the problem.
How long should I pause my campaign for?
48 hours. Do not send anything during this window.
What if my bounce rate is still high after following all 5 steps?
Reach out to support via the chat icon at the bottom right of your dashboard, or tag the team in the VIP community. They will investigate your specific setup.
Why does restarting ramp-up matter so much?
Jumping straight back to full sending volume after a bounce spike repeats the exact behavior that triggered Google to flag your inboxes in the first place. The gradual ramp-up rebuilds trust with the inbox provider over several days.
Is a bounce rate under 5% considered normal?
Yes. Some bounces are a normal part of cold email at volume. The goal is not zero bounces, it is keeping the rate under 5% and acting quickly if it spikes above that.
What falls under a hard bounce vs a sender bounce?
A hard bounce means the lead's email address itself is invalid. A sender bounce means Google blocked the email due to your sending pattern, even though the lead's email may be perfectly valid. The 5-step protocol addresses both.