23% of B2B domains are catch-all servers. Without detection, these look valid but bounce at 40-60% rates. BounceZero identifies catch-all domains with 3-probe SMTP fingerprinting - not just a flag, an estimate.
A catch-all server says “yes” to every address you test - even ones that don’t exist. That yes is worthless without deeper analysis.
A catch-all mail server accepts RCPT TO for any address at the domain. Basic verifiers mark these "valid" and you find out the truth when 40-60% of them hard bounce.
Nearly a quarter of business domains run catch-all configurations - Microsoft 365 tenants, Google Workspace, and security gateways like Proofpoint and Mimecast are common culprits.
Mailbox providers track your bounce rate per sending domain and IP. Cross 2% and deliverability drops for your entire list - including the genuinely valid addresses.
Every address passes through six verification layers. For catch-all domains, we go further - probing server behavior to estimate real deliverability instead of shrugging with an “unknown.”
We probe the mail server with the real address plus randomized non-existent addresses, comparing response codes, timing, and banner behavior to fingerprint catch-all configurations.
Direct SMTP-level verification that the specific mailbox exists - not just that the domain accepts mail.
Full DNS inspection of MX, TXT, and DMARC records to identify the mail provider and known catch-all-prone gateways.
Temporary and burner domains flagged instantly, before they pollute your list with addresses that expire in minutes.
Addresses like info@, sales@, and admin@ identified - these convert poorly and generate spam complaints on catch-all domains.
Known and suspected spam trap patterns detected - one trap hit on a catch-all domain can blocklist your sending IP.
From upload to a segmented, send-ready list in minutes - 10K emails process in 5-10 minutes.
Drag in a CSV of up to 1,000,000 addresses per dashboard job, or verify in real time via our REST API with provider-dependent response time.
We resolve MX, DMARC, and provider records for every domain, identifying mail infrastructure known to run catch-all configurations.
For each domain, we test the real address alongside randomized fake addresses. Identical acceptance behavior confirms a catch-all; response timing and code patterns feed the deliverability estimate.
Catch-all addresses get an estimated deliverability score built from 65+ verification and metadata fields - not a lazy "unknown" flag that leaves you guessing.
Export valid, catch-all-scored, and invalid segments separately. Send to high-confidence catch-alls, suppress the rest, and keep your bounce rate under 0.5%.
Other services charge extra for catch-all analysis or return “unknown” and bill you anyway. Every BounceZero verification includes full 3-probe fingerprinting.
A catch-all domain is configured to accept mail sent to any address at that domain, whether or not the mailbox actually exists. The server responds "accepted" during SMTP verification for real and fake addresses alike, which makes standard email verification unreliable. Around 23% of B2B domains run catch-all configurations.
We use 3-probe SMTP fingerprinting: alongside the address you want to verify, we test randomized addresses that cannot exist at the domain. If the server accepts them all, it is a catch-all. We then analyze response codes, timing patterns, and provider infrastructure across 65+ verification and metadata fields to estimate whether your specific address is actually deliverable.
Not with a simple yes/no - but they can be scored. BounceZero returns a deliverability estimate for every catch-all address rather than a flat "unknown," using domain intelligence, mailbox pattern analysis, and server behavior fingerprinting. That lets you segment high-confidence addresses from risky ones instead of discarding a quarter of your list.
Selectively. Sending to all catch-all addresses blindly produces 40-60% bounce rates on the bad ones, which damages sender reputation. The right approach is to send only to catch-all addresses with a high deliverability estimate and suppress or drip-test the rest - exactly the segmentation BounceZero exports give you.
BounceZero delivers 99.8% overall verification accuracy, compared to the ~95% industry benchmark. Cleaned lists typically see bounce rates below 0.5%. Catch-all fingerprinting uses multiple probes and retry logic to avoid the false positives that fool single-probe verifiers.
Yes. Every verification - API or bulk - includes full 3-probe catch-all fingerprinting at $3 per 1,000 emails. You also get 100 free verifications per month with no credit card required, so you can test it on your own list first.
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 every month - no credit card required.
Start Verifying Free100 free verifications/month - No credit card - provider-dependent API response time
Single-email checks, no signup required
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Free email bounce rate calculator: enter your list size and expected bounce rate to see the real
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