Catch-all domains accept email for every address — real or invented. Standard verification can't detect this. BounceZero uses a 3-probe SMTP method to fingerprint catch-all behavior and score the delivery risk accurately.
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A catch-all (or accept-all) domain is configured to accept email for every address at that domain — whether the mailbox exists or not. The server returns a "250 OK" to any RCPT TO command, regardless of whether the user exists.
This makes standard single-probe SMTP verification unreliable. A server might accept real.user@company.com and doesnt.exist.xyz@company.com with the exact same response.
BounceZero detects this by sending 3 probes with invented addresses. If all are accepted, the domain is flagged as catch-all and classified as Risky.
23% of B2B corporate domains are catch-all. Sending to these without detection means your bounce rate won't reflect the true picture — until the provider starts penalizing your domain.
A single SMTP probe can't detect catch-all. BounceZero runs three probes with invented random addresses to fingerprint the server's behavior.
BounceZero sends an SMTP RCPT TO for a random invented username at the target domain (e.g., xz7q9p4m@company.com). If the server accepts it, catch-all is suspected.
A second invented address is tested. Both accepted? Catch-all confidence rises significantly. The server has now accepted two non-existent mailboxes.
A third probe confirms the pattern. If all three invented addresses are accepted, the domain is classified as catch-all with high confidence. BounceZero marks the result as Risky.
Catch-all addresses are classified as Risky rather than Valid or Invalid. BounceZero provides a confidence score and AI-powered reasoning to help you decide whether to include them in your campaign based on your risk tolerance.
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