Smartlead distributes sends across multiple inboxes - but one bad list can burn them all. BounceZero strips invalid addresses before you queue your first follow-up.
100 free verifications/month - No credit card required
Smartlead's inbox rotation spreads your volume for safety - but it also spreads your bounces. A bad list doesn't damage one mailbox; it damages the whole rotation.
Smartlead round-robins your list across every connected inbox. Upload a list with 5% bad addresses and every mailbox in the rotation takes reputation damage - there's no safe inbox left to fall back on.
Smartlead's warm-up builds sender reputation over weeks. A single bounce spike above ~2% can undo it in a day, throttling your entire fleet before your AI sequences finish their first pass.
Roughly 23% of B2B domains are catch-all - they accept everything, then bounce or drop it later. Simple checkers mark them "valid"; BounceZero's 3-probe test tells you which ones actually deliver.
Each address runs through six verification layers at up to 99.8% accuracy in internal testing on SMTP-verifiable addresses - well above the industry benchmark of ~95%.
Live SMTP-level confirmation that the inbox actually exists - the single biggest predictor of a hard bounce in your Smartlead campaigns.
Our triple-probe test separates genuinely deliverable addresses from catch-all domains that accept everything and bounce later mid-sequence.
Flags info@, sales@ and admin@ addresses that rarely reply to cold outreach and often trigger the spam complaints that sink inbox rotations.
Removes temporary and throwaway inboxes that inflate your lead count while contributing zero replies to your Smartlead pipeline.
Confirms the domain can actually receive mail before Smartlead wastes a rotation slot - and a reputation hit - sending to it.
Identifies known and suspected spam traps that can get every domain behind your Smartlead inboxes blocklisted in a single send.
Five minutes of verification protects every inbox in your rotation. Here's the workflow Smartlead users run with BounceZero.
Pull your leads as CSV from your data source - Apollo, Clay, LinkedIn scrapes, purchased lists - or export an existing lead list from a Smartlead campaign.
Drag your CSV into the bulk verifier. Up to 1,000,000 addresses per dashboard job - a typical 10K cold email list finishes in 5-10 minutes.
Mailbox existence, 3-probe catch-all, role, disposable, MX and spam trap detection run on every address at up to 99.8% accuracy in internal testing on SMTP-verifiable addresses.
Get your list back split into deliverable, risky and invalid. Keep the deliverable segment; quarantine or drop the rest.
Upload only verified addresses to your Smartlead campaign. Your bounce rate stays under 0.5%, and every inbox in your rotation keeps its warm-up reputation intact.
Replacing burned Smartlead inboxes means new domains, new mailboxes and 2-3 weeks of warm-up - multiplied across your whole rotation. Verification costs a fraction of that.
Common questions from cold email teams verifying lists before Smartlead.
Yes - via a simple CSV workflow or our API. Export your leads, upload them to BounceZero, and import the cleaned deliverable segment back into your Smartlead campaign. For automated pipelines, our REST API (provider-dependent response time) can verify leads programmatically before they ever reach a Smartlead lead list.
Always before. Once Smartlead sends to an invalid address, the bounce has already damaged the reputation of whichever inbox in your rotation drew that send - and no tool can undo it. Verifying first means only deliverable addresses ever enter your campaigns, keeping bounce rates under 0.5%.
No - it does the opposite. Rotation spreads a dirty list's bounces across every connected inbox, so instead of burning one mailbox you degrade the entire fleet at once. Rotation protects you from volume limits, not from bad data. Verification is the only thing that keeps invalid addresses out of the queue.
Around 23% of B2B domains are catch-all, and basic checkers mark them all "valid". BounceZero's 3-probe catch-all detection scores how likely each one is to actually deliver. Send to high-confidence catch-alls from a secondary Smartlead campaign with its own inboxes, and keep unverifiable ones out of your primary rotation.
A 10,000-email list finishes in about 5-10 minutes through the bulk verifier, and single dashboard jobs scale up to 1,000,000 addresses. You can export from your data source, verify, and load a clean list into Smartlead within the same working session - before your first follow-up is ever queued.
$3 per 1,000 verifications - so a 10K-lead campaign costs about $30 to clean. Every account also includes 100 free verifications per month with no credit card required, so you can test accuracy on your own list before paying anything.
up to 99.8% accuracy in internal testing on SMTP-verifiable addresses. $3 per 1,000 verifications. Results in seconds. Start with 100 free verifications - no credit card required.
Verify your list before loading it into your sending platform
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