Catch-All (Accept-All) Domain Checker
Verify whether a destination mail server accepts any incoming email regardless of username. Real-time live probing with DNS MX resolution and cached intelligence.
The 4 Possible Mail Server States We Diagnose
A simple boolean is not enough. Our engine connects to the remote MTA and categorizes the domain into four precise technical states:
1. Catch-All (Accept-All)
250 OKThe server accepts simulated handshakes for non-existent randomized addresses. Downstream messages may be redirected to a central administrative queue, silently purged, or generate delayed bounces.
2. Strict (Not Catch-All)
550 RejectedThe destination MTA validates recipient usernames in real time and explicitly rejects unknown mailboxes with 550 User Unknown. Mailbox existence can be verified definitively.
3. Invalid / No Mail Server
No MX / RFC 7505The domain has no operational MX or A records configured to receive mail, or advertises an explicit "Null MX" record (.) indicating the domain does not accept email.
4. Unknown (Unresponsive)
Timeout / 421The mail server timed out, dropped the TCP connection, or applied temporary greylisting rate-limits (421/451). NullBounce returns is_catch_all: null to prevent false assumptions.
Free Catch-All Tool vs. Full NullBounce Platform
This lookup diagnoses domain-level configuration. For complete contact hygiene and specific mailbox deliverability, use our full engine.
| Verification Feature | This Free Tool | Full Platform (Bulk/API) |
|---|---|---|
| Domain Catch-All & Accept-All Diagnostic | ✓ Included | ✓ Included |
| Input Query Type | 1 Email or Domain | CSV, TXT, or REST API |
| MX Route & Null MX (RFC 7505) Check | ✓ Included | ✓ Included |
| Specific Mailbox Existence Check (Does user exist?) | ✕ No | ✓ Included |
| Disposable & Burner Domain Detection | ✕ No | ✓ Included |
| Role-Based Account Flagging (info@, sales@) | ✕ No | ✓ Included |
| Bulk Upload (Up to 100,000+ contacts per batch) | ✕ No | ✓ Included |
Should You Send Cold Outreach to Catch-All Domains?
Between 15% and 30% of typical B2B prospect lists (scraped from Apollo, LinkedIn, or ZoomInfo) belong to catch-all domains. Businesses enable accept-all routing primarily to prevent losing inbound sales inquiries caused by customer typos.
However, for cold emailers, catch-all domains represent an unpredictable deliverability hazard. While the receiving server returns a 250 OK handshake initially, internal mail routers often fail to find the recipient employee. Depending on the company's internal IT policy, the message may be silently routed to an unmonitored administrator junk folder or bounced days later.
Best Practice: When sending cold outreach from your primary corporate domains, send exclusively to Safe (Deliverable) contacts. If you decide to contact Catch-All addresses, segment them into dedicated secondary domains with strict daily sending limits (under 30 emails/day per inbox) to insulate your main reputation. For an in-depth breakdown, read our Catch-All Email Guide.
Catch-All Checker: Frequently Asked Questions
Practical answers about accept-all mail servers and verification limits.
Can an email verifier guarantee delivery to a catch-all email?
No verification service in the world can guarantee 100% deliverability for catch-all emails without actually delivering an email. Because the server accepts all usernames indiscriminately, downstream routing happens internally. NullBounce accurately flags them as Risky so you can manage your campaign risk tolerance.
What does the "Unknown" catch-all status mean?
An Unknown status (is_catch_all: null) occurs when the remote mail server fails to respond within the socket timeout window or applies temporary greylisting throttling (421/451 response codes). We never guess: Unknown means the server was temporarily unreachable.
Does checking a domain send an email to the company?
No. Our engine connects to the mail server via SMTP, tests how the server responds to the probe handshake, and safely aborts the session before any email data or body content is transmitted. The domain administrator receives no email.
How can I clean a list with thousands of Catch-Alls?
Upload your full CSV file to our Bulk Email Verifier. NullBounce tags every address clearly (Safe, Invalid, Risky, or Unknown) and keeps your original CSV columns intact so you can filter out Risky Catch-Alls with a single click.
Isolate Risky Catch-Alls Across Your Entire Database
Sign up today and get 100 free verification credits. Upload your CSV and download clean, VLOOKUP-ready prospect lists.
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