TL;DR
- lemlist alerts at a 10% bounce rate and auto-pauses at 50%, once 100 leads have been contacted.
- lemlist's own advice is to pause above 5% and stay under 3%, so the automatic safety net is far looser than the target.
- lemlist's verifier costs 1 credit ($0.01) per lead. MailExchange costs $0.0058 or less, credits never expire, and unknowns are refunded.
Why lemlist's bounce limits won't protect your domain
lemlist's help center says bounce alerts fire at 10% and campaigns pause automatically at 50% once at least 100 leads have been contacted. On a list of 1,000 leads, that means hundreds of bounces could land before anything stops on its own.
The same article tells you to pause an active campaign yourself if bounces pass 5%, and to keep them under 3%. Mailbox providers judge your sending domain long before lemlist's 50% switch would trip. The only reliable way to stay under 3% is to take dead addresses out before the first email goes.
More on how quickly bounces damage a domain: how many bounces before a domain is burned?
How to verify leads for lemlist
- Export your leads as a CSV from your lead source (Apollo, Clay, a vendor list) or from an existing lemlist campaign.
- Upload the CSV to MailExchange. Duplicates are removed free, and every row gets a state and a reason. Your other columns are kept, so personalisation variables survive.
- Filter the results. Keep deliverable rows, drop undeliverable ones, and decide what to do with risky rows (below).
- Import the clean CSV into lemlist. You don't need to spend lemlist credits verifying the same leads a second time.
Catch-alls, role addresses and other risky leads
lemlist puts catch-all ("Accept All"), full-mailbox and disposable addresses under Risky, and often marks role addresses as undeliverable. MailExchange splits risky leads by reason, so you can treat each kind differently:
- Catch-all (
low_deliverability): the domain accepts every address, so the server's "yes" proves nothing. Send these from a separate, slower campaign on your oldest domains, or skip them on new ones. - Role (
low_quality): info@, sales@ and similar. Usually real inboxes, but rarely the person you want and more likely to complain. - Disposable: drop them.
More detail: should you send to catch-all emails?
Cost: lemlist credits vs MailExchange
| Option | Cost per lead verified | 10,000 leads | Unknowns refunded? |
|---|---|---|---|
| lemlist email verification (1 credit) | $0.01 | $100 | Not stated |
| lemlist Finder & Verifier (5 credits) | $0.05, charged on deliverable or risky results | up to $500 | Charged only on deliverable or risky |
| MailExchange 5K / 10K | $0.0058 / $0.0049 | $49 | Yes, and duplicates are free |
| MailExchange 100K | $0.0030 | n/a | Yes |
lemlist figures from lemlist credits, Finder & Verifier and reducing bounces, checked 2026-10-17. Run your own numbers with the verification cost calculator.
Re-verify before long sequences
Lists decay. People leave jobs mid-sequence, and bounce rates often climb on later steps. If a list is more than a few weeks old, export it from lemlist, run it through MailExchange again, and remove anyone who has turned undeliverable before the next step goes out.
Automate it with the API
If leads reach lemlist from a script or Clay, call the MailExchange API first (early access) and push only the leads you want with lemlist's add-lead-to-campaign API call. A direct lemlist connector is on our roadmap. Ask for an API key.