SieveSieve vs ZeroBounce
We built this comparison, so assume bias. That is exactly why the rows where ZeroBounce wins are still in it. Where they are genuinely better, we say so.
ZeroBounce is one of the longest-running email verification services, with a large customer base and a broad catalog of one-click integrations for tools like Mailchimp and HubSpot. It verifies mailboxes over live SMTP, like everyone here, and returns a sub-status on each result. Where Sieve differs is evidence and privacy: every Sieve verdict ships with the MX host that answered and the raw SMTP reply code, catch-all domains get a 0 to 100 confidence score instead of a yes or no flag, and your list is verified on single-tenant infrastructure that never pools your data with other customers.
Price per 1,000 verifications at ~10k volume
Published list prices, June 2026. Check vendor sites for current rates. Sieve pack math: $5/1k = $5.00, $19/5k = $3.80, $69/25k = $2.76, $169/100k = $1.69, $29 Pro / 15,000 = $1.93 per 1,000.
Sieve vs ZeroBounce, capability by capability
| Capability | Sieve | ZeroBounce |
|---|---|---|
Live SMTP mailbox verification Table stakes: both do it. | ||
Verdict receipt on every address The MX host that answered and the SMTP reply code, in the API response. | ||
Catch-all confidence score (0 to 100) Built from real probe evidence. | Binary catch-all flag | |
Detects full and disabled mailboxes From the live SMTP reply code, shown on the receipt. | Quota-exceeded sub-status, no reply code shown | |
Pre-send risk verdict Fuses the recipient verdict with YOUR sending domain's SPF, DKIM and DMARC health into one send, caution or suppress call. | ||
Single-tenant, self-hosted privacy Your lists never leave our EU-jurisdiction box, are never resold, and never train a pooled cross-customer dataset. | Multi-tenant cloud | |
Established brand and prebuilt integrations One-click app connectors for common marketing and CRM tools. | Newer; API, MCP server and widget, fewer one-click app integrations | Large integrations directory |
Free tier | Unlimited DNS checks + 100 live SMTP/mo | Trial credits |
Competitor capabilities summarized from their public docs, June 2026. One caveat that applies to both of us: free-mail providers (Gmail, Yahoo, Outlook, iCloud) block mailbox probing. No vendor can truly SMTP-verify those addresses, whatever the marketing says.
The honest tradeoff
ZeroBounce is the more established brand with more prebuilt integrations. Sieve gives you the evidence behind every verdict, catch-all confidence scores and single-tenant privacy, usually at a lower price per 1,000.
Judge us before you pay anything
Grade your sending domain's deliverability free: MX, SPF, DKIM, DMARC, blacklists. No signup.
Then verify a list with receipts
Unlimited DNS checks plus 100 live SMTP verifications a month, free. Every paid verdict ships with its evidence.
Frequently asked questions
Is Sieve a good ZeroBounce alternative?
Yes, if you want to see the evidence behind each verdict rather than just a status label. Sieve returns the MX host and SMTP reply code on every address, scores catch-all domains 0 to 100, and runs on single-tenant infrastructure that never pools your list with other customers, usually at a lower price per 1,000. ZeroBounce is the stronger pick if you rely on its large directory of one-click integrations.
Is Sieve cheaper than ZeroBounce?
At around 10,000 addresses, ZeroBounce's published credit pricing works out to roughly $7 to $8 per 1,000, while Sieve's credit packs and Pro plan land below that. Both get cheaper per 1,000 as volume rises, so check the current pack prices on the pricing page for your exact list size.
What does Sieve do that ZeroBounce does not?
Three things stand out: a verdict receipt on every address (the MX host that answered plus the raw SMTP reply code), a catch-all confidence score from 0 to 100 instead of a binary catch-all flag, and a pre-send risk verdict that folds your own sending domain's SPF, DKIM and DMARC health into the call. Sieve is also single-tenant, so your list never joins a shared cross-customer dataset.
Can I verify a list with Sieve for free?
Yes. Sieve's free plan includes unlimited DNS-layer checks plus 100 live SMTP verifications every month, with no credit card, so you can test it on a sample of your list before paying anything.