Catch-All Domain
What is Catch-All Domain?
A mail server configured to accept incoming SMTP `RCPT TO` requests for any local-part at that domain (`[email protected]`) during the initial connection, even if the specific individual mailbox does not exist.
Why Catch-All Domain Matters in Production
Over 40% of B2B corporate domains configure catch-all acceptance (or enterprise gateways like Proofpoint and Mimecast) to prevent directory harvesting. Mailing unsegmented catch-all lists alongside verified contacts often causes delayed bounce notifications (NDRs) that push bounce rates above 5%.
Engineering & Sender Best Practices
- • Never mix `CATCH_ALL` contacts with `VALID` contacts on your primary cold outreach domains.
- • Cross-reference `CATCH_ALL` prospects against recent LinkedIn job-change signals or website activity before sending.
- • On SaaS signup forms, fail open (allow `CATCH_ALL` users through) and confirm ownership via magic link or OTP.
- • Send to `CATCH_ALL` segments from isolated secondary domains at 15–25 emails/day per inbox.
Segmenting Enterprise B2B Leads Without 10x Credit Multipliers
A B2B demand-gen agency auditing 100,000 mid-market and enterprise leads found that 28,400 addresses belonged to catch-all domains behind Mimecast, Proofpoint, or Microsoft 365 wildcard routing. Instead of paying $300–$800 on legacy "catch-all scoring" tools or deleting 28% of their TAM, they verified all 100K rows on MailVeri for a flat $59 (1 credit per check) and routed CATCH_ALL leads to secondary burner domains.
Technical Implementation & Wire Example
{
"email": "[email protected]",
"status": "CATCH_ALL",
"domain": "enterprise-saas.io",
"mx_host": "mxa-001234.gslb.pphosted.com",
"credits_used": 1,
"routing_policy": "secondary_catch_all_domain"
}MailVeri detects catch-all server behavior at 1 flat credit (no 10x credit multiplier) so you can isolate accept-all prospects.
MailVeri 7-Status Verification Reference & Sender Action Matrix
Keep Campaign Bounces < 2%| Status | Technical Meaning | Bounce Risk | Recommended Sender Action |
|---|---|---|---|
| VALID | Mailbox exists and actively accepts mail | < 0.5% (Safe) | Safe for cold outbound, newsletters, and transactional sends |
| INVALID | Syntax error, dead MX, or 550 mailbox does not exist | 100% Hard Bounce | Suppress immediately; block at signup |
| DISPOSABLE | Temporary burner address (100,000+ tracked domains) | High / Fake User | Reject at signup form; purge from CRM |
| CATCH_ALL | Domain accepts all mail regardless of local-part | 12–28% Deferred | Isolate to secondary sending domains; allow on SaaS signup |
| ROLE_ACCOUNT | Verified shared inbox (info@, support@, sales@) | Complaint Risk | Skip in 1-on-1 cold email; allow if opted in |
| FULL_INBOX | Recipient mailbox exceeded storage quota (452 / 552) | Soft / Hard Bounce | Pause sends for 30 days and re-verify before mailing |
| UNKNOWN | Transient mail server deferral or timeout (0 credits billed) | Unverified | Fail open on signup; re-verify via bulk batch before cold blast |
Catch-All Emails Explained: How to Detect & Segment Accept-All Domains →
Why B2B domains use accept-all configurations and how to mail catch-all leads without burning your sender reputation.
Free Verification & Address Types Tools & Workflows
Frequently Asked Questions About Catch-All Domain
How does an email verifier detect a catch-all domain during an SMTP check?
Before or alongside probing the target address, the verifier sends an RCPT TO command for a cryptographically random, non-existent local-part at the same domain (e.g., [email protected]). If the mail server replies 250 OK to the random string, the domain is classified as CATCH_ALL.
Why do catch-all domains still bounce hours after accepting an email?
Enterprise secure email gateways (Proofpoint, Barracuda, Mimecast) accept all messages at the perimeter MTA to inspect content first, then forward the message to the internal Exchange or Google Workspace directory. If the internal user no longer exists, the internal server sends a delayed NDR bounce.
Does MailVeri charge extra credits for catch-all domain checks?
No. MailVeri charges 1 flat credit per verification ($0.0002–$0.0009) regardless of whether the target domain is a standard mailbox or a catch-all server.
Closely Related Terms
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