ZeroBounce

What it is

ZeroBounce is a standalone email verification service. You give it a list or an API call, and it returns a status for each address: valid, invalid, catch-all, unknown, spam trap, abuse or do-not-mail, plus sub-statuses such as disposable or role-based. Its second product is A.I. Scoring, which gives each address a quality score from 0 to 10 and is meant mostly for catch-all domains, where an SMTP check can’t tell whether the mailbox exists. Around those two it sells deliverability tools: inbox placement tests, blacklist monitoring, DMARC monitoring, warmup seeds and an email finder.

The company was founded in 2017, is based in Santa Barbara, California, and reports more than 650,000 customers. It holds SOC 2 Type 2 certification and deletes uploaded files within 30 days.

The question this page answers: which verifier should sit between your list source and Smartlead or Instantly to keep bounces under 2%? Instantly’s 2026 email verification benchmark (updated 2026-01-31) uses 2% total bounces and 1% hard bounces as the line before inbox providers start flagging a sender, and it named ZeroBounce the pick for buyers who want standalone accuracy and can absorb the cost. Our answer: ZeroBounce when catch-alls are a large share of your list or you need a SOC 2 vendor, MillionVerifier when cost per address decides it.

Why it shows up in RevOps stacks

• It does something with catch-alls. Most B2B lists carry catch-all domains that basic verifiers mark “risky” and leave to you. ZeroBounce’s scoring docs publish example bounce rates by score for catch-all addresses: about 1.3% at a score of 10, 5% at 7 and 20% at 4. That gives you a cut-off you can set instead of sending all catch-alls or none.
• You don’t pay for unknowns. “Unknown” results and duplicates removed from a list are not charged. ZeroBounce reports an unknown rate of 1.75% for 2025.
• It plugs into the places lists come from. There is a native HubSpot integration (CRM and forms), a native Clay enrichment (Clay’s managed account at 1 Clay credit per email, or your own API key), Zapier, and a local MCP server (npm package @zerobounce/mcp) with 15 tools for validation, bulk files, scoring, finder and credit checks, which works with Claude Desktop, Cursor and VS Code. There is no native connector for Smartlead or Instantly: you verify before upload, by CSV or API.

Pricing reality

There is a free plan with 100 validations a month. Pay-as-you-go starts at $39 for 2,000 credits ($19.50 per 1,000). The ZeroBounce ONE subscription starts at $99 a month for 10,000 credits, and annual billing takes 20% off. While a subscription is active, unused credits roll over and don’t expire. Without one, expiry depends on your account and purchase dates, so check the terms before buying a large pay-as-you-go block.

Volume tiers, as recorded by Emelia on 2026-09-07: pay-as-you-go 10,000 credits for $129, 100,000 for $649 ($6.49 per 1,000) and 1,000,000 for $3,199. Subscription 25,000 a month for $199, 100,000 for $449 ($4.49 per 1,000). Scoring costs 1 more credit per address, so validating and scoring a catch-all costs 2 credits.

What a cold-email team actually pays: verifying 50,000 new addresses a month costs about $380 a month on ONE, or roughly $4,500 a year before the annual discount. The same volume on MillionVerifier, which lists 50,000 credits for $89 with credits that never expire, is about $1,070 a year. So ZeroBounce costs about 4 times as much at this volume, and you are paying for catch-all scoring, the deliverability tools and the compliance paperwork.

Best for

RevOps and outbound leads at B2B teams sending 20,000 to 500,000 cold emails a month, where catch-all domains are more than about 15% of the list, bounces have already cost a sending domain, and security review needs a SOC 2 vendor. Also for marketing ops teams cleaning HubSpot contacts at form fill.

Don’t buy it if your list has few catch-alls and the only question is valid or invalid at the lowest price: MillionVerifier does that for about a quarter of the cost. Don’t buy it if you send fewer than about 5,000 new contacts a month from Instantly or Smartlead, where the sequencer’s built-in verification is enough.

Versus the alternatives

MillionVerifier is the budget pick: 50,000 credits for $89, 1 million for $449, credits that never expire, catch-all verification included and refunds on addresses it can’t verify. Pick it for high-volume, low-catch-all lists. Instantly’s benchmark notes weaker catch-all detection and reported problems with Yahoo addresses, so test it on your own sample.

NeverBounce is the other long-established standalone verifier, at about $8 per 1,000 pay-as-you-go, with credits that expire 12 months after purchase. Pick it if your team already runs its CRM sync and catch-all scoring doesn’t matter to you, because NeverBounce labels catch-alls without scoring them.

Built-in sequencer verification is the option taking share: Instantly verifies at 0.25 credits per lead and blocks invalid and risky leads by default, and Smartlead sells a verification add-on at upload. Pick it when volume is low and one less vendor matters more than catch-all control.

If none of them fit, the problem is usually the list source, not the verifier. Fix sourcing first with waterfall enrichment through Clay, FullEnrich or Prospeo, then place the verifier where the cold email infrastructure stack shows it.

Watch-outs

• The 99.6% accuracy claim is the vendor’s. ZeroBounce’s own July 2026 benchmark reports 98.0% on a hard-to-validate list, and competitor-run tests report lower. Guard: before committing, run a 2,000-address sample from your own sources through ZeroBounce and one alternative, send to the addresses both mark valid, and compare hard-bounce rates.
• Scoring is not covered by the guarantee. ZeroBounce’s validation guarantee does not extend to A.I. Scoring, and a score of 4 still bounces about 1 in 5. Guard: start sending catch-alls at a score of 10, go down one point at a time, and stop at the score where bounces pass 2%.
• Pay-as-you-go credits can expire. Only an active ONE subscription guarantees rollover. Guard: buy pay-as-you-go blocks no larger than 3 months of usage, or move to ONE once monthly volume is steady.
• No direct path into the sequencer. Verification happens before upload, so addresses that sit in a campaign for weeks age. Guard: re-verify any list older than 30 days before it goes into Smartlead or Instantly, and keep the verification date as a field on the lead. Email deliverability for cold outreach covers the rest of the sending setup.