centrum.cz: mail servers, SPF, DMARC, DKIM and reputation

Mail servers for centrum.cz

DNS lists 4 mail hosts for centrum.cz, starting with centrum-cz-10mx1.eco-mx.cz. Lower priority values are tried first; the rest exist for failover.

Who runs the mail

The hosts match the pattern of an unrecognised provider. The mail hosts do not match a known provider pattern, so the domain is probably self-hosted or on a smaller provider. Catch-all behaviour varies from server to server, which is exactly why a mailbox-level probe, not the MX record, decides whether an address exists.

What this means for verification

For centrum.cz, verification runs the whole pipeline: syntax, live MX, the open lists, and then the SMTP handshake with the mail host, with no message ever transmitted. Each verdict carries a machine-readable reason.

SPF for centrum.cz

centrum.cz publishes an SPF record; it names its senders directly rather than through include mechanisms, and the record has no explicit all mechanism, so receivers treat unlisted servers as neutral.

DMARC for centrum.cz

centrum.cz has DMARC in monitoring mode (p=none). Receivers report what they see but deliver failing mail anyway, so the record protects nothing yet.

Why it matters

Receivers use SPF, DKIM, and DMARC together to decide whether a message really came from centrum.cz. A domain with a strict SPF record and an enforcing DMARC policy is hard to spoof and easier to deliver for; one without either is neither. Spaw reports has_spf and dmarc_policy on every lookup and adds a small risk weight when SPF is missing.

DKIM keys for centrum.cz

3 DKIM selectors found for centrum.cz (s1, s2, mail). Each is a public key in DNS that receivers use to check the signature on messages from centrum.cz; together with SPF it is what a DMARC policy enforces.

What the check reads

DKIM keys live in DNS at <selector>._domainkey.centrum.cz, one TXT record per selector, and the selector is chosen by whoever signs the mail. This checker asks for the selectors the large providers and sending platforms use by default (google, selector1 and selector2 for Microsoft 365, k1, s1, fm1 and about thirty more), so a key found here is a real key, and a key not found here may simply sit under a name the list does not know.

How it fits with SPF and DMARC

centrum.cz has DMARC in monitoring mode (p=none). Receivers report what they see but deliver failing mail anyway, so the record protects nothing yet. centrum.cz publishes an SPF record; it names its senders directly rather than through include mechanisms, and the record has no explicit all mechanism, so receivers treat unlisted servers as neutral.

Transport security for centrum.cz

centrum.cz publishes no an MTA-STS policy record record at _mta-sts.centrum.cz. Without MTA-STS, a sender that cannot negotiate TLS with the mail host may fall back to delivering in the clear, and an attacker on the path can force exactly that. centrum.cz publishes no a TLS-RPT record record at _smtp._tls.centrum.cz. TLS-RPT would give the domain owner a daily report of delivery attempts that could not establish TLS; without it, failures are invisible.

Brand indicators for centrum.cz

centrum.cz publishes no a BIMI record record at default._bimi.centrum.cz. BIMI is optional and mostly cosmetic; it only becomes possible once DMARC enforces quarantine or reject.

SPF details for centrum.cz

centrum.cz publishes SPF. The policy's all qualifier is ?all (neutral: unlisted servers are neither authorised nor refused). Evaluating it takes 1 DNS lookup, within the ten RFC 7208 allows.

DMARC details for centrum.cz

centrum.cz has DMARC in monitoring mode (p=none). Receivers report what they see but deliver failing mail anyway, so the record protects nothing yet. The policy applies to all of the domain's mail (pct=100). Aggregate reports are collected (rua= is set), so the owner sees who sends as the domain.

Is centrum.cz disposable?

centrum.cz is a consumer email service rather than a company domain: real people, personal accounts, and no way to infer an employer from the address.

About the domain

Its mail is handled by an unrecognised provider.

How Spaw treats addresses at centrum.cz

For centrum.cz, verification runs the whole pipeline: syntax, live MX, the open lists, and then the SMTP handshake with the mail host, with no message ever transmitted. Each verdict carries a machine-readable reason.

Common questions about centrum.cz

Does centrum.cz accept mail?

centrum.cz accepts mail through a third-party mail host.

Does centrum.cz publish SPF and DMARC?

centrum.cz publishes SPF ending in ?all and a DMARC policy of none.

Is centrum.cz a disposable, relay or free-provider domain?

centrum.cz is a free mailbox provider, so an address there is a consumer inbox rather than a company's.

Does centrum.cz publish DKIM, MTA-STS, TLS-RPT or BIMI?

centrum.cz does not publish MTA-STS, does not publish TLS-RPT and does not publish BIMI. DKIM keys were found under the selectors s1, s2, mail.

Where does this report come from?

Live DNS, the open disposable, role and free-provider lists, the registry's RDAP record and the threat blocklists the IP product installs, read on 2026-10-24 and cached for a week. Nothing here says anything about a person; it describes the domain's mail setup on that day.

Check another domain

• Email checker
• MX record lookup
• SPF & DMARC checker
• Disposable email domain checker
• DKIM checker
• MTA-STS, TLS-RPT and BIMI checker
• The same answer over the API: GET /api/v1/email/domain/centrum.cz