DMARCレコードチェッカー

_dmarcサブドメインのDNS検証：ポリシー強度、SPF/DKIMアライメント要件、集約レポート（RUA）設定の診断。

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IncogSay Privacy & Stateless Architecture Guarantee

Stateless edge execution • Zero database retention • No user tracking or behavioral profiling

Zero-Log Verified

1Stateless Edge V8 Isolates

Every network lookup executes inside a temporary, isolated V8 sandbox deployed across Cloudflare's global edge. Each isolate is instantiated on demand, parses public DNS or TLS socket records in transient RAM, returns the result stream, and terminates immediately.

2Zero Query & IP Retention

IncogSay operates under a strict zero-retention guarantee. Target domains, submitted URLs, and user IP addresses are never written to disk, stored in relational databases, or logged in persistent files. We do not maintain historical query logs or link lookups to user identities.

3No Accounts, No Tracking Cookies

All tools are completely free and functional without registration, user logins, or account creation. We never deploy invasive session fingerprints, third-party analytics trackers that capture input payloads, or behavioral profilers. Your queries remain ephemeral and anonymous.

Compliance: Audited under GDPR Art. 5(1)(e) (Storage Limitation) & CCPA/CPRA Privacy Principles.Read full architecture documentation →

Operational Workflow — DMARCレコードチェッカー

4-Stage Diagnostic Execution

対象ドメイン名を入力します。
「DMARCを確認」をクリックして_dmarcレコードを取得します。
ポリシー設定（p値）がnone、quarantine、rejectのいずれであるか確認します。
なりすましメールを監視するためのruaメールアドレスが登録されているか確認します。

DMARC運用の段階的アプローチ

いきなりp=rejectを設定すると正当な外部システムからの配信まで拒否される恐れがあります。まずはp=noneでレポートを収集・分析し、全正当送信元を網羅した段階でquarantine、最終的にrejectへと移行するのが推奨手順です。

Email Authentication Architecture & RFC Verification Standards

Enterprise email delivery relies on a four-tier cryptographic and policy stack. This tool executes statelessly against public authoritative nameservers to audit each protocol layer in real time.

1RFC 7208 — SPF Envelope Validation

Validates the Return-Path against designated sending MTA IP ranges. Strictly calculates recursive lookup depth against the 10-DNS-query boundary to prevent delivery-breaking permerror statuses.

2RFC 6376 — DKIM Public Key Cryptography

Retrieves public RSA (2048-bit minimum) or Ed25519 public keys at selector DNS records, ensuring cryptographic non-repudiation and transit tamper detection for canonicalized body hashes.

3RFC 7489 — DMARC Policy Alignment

Enforces strict alignment between the visible From domain and SPF/DKIM authenticated identifiers. Dictates receiver disposition across none, quarantine, and reject policies.

4RFC 8461 & BIMI — Transport Encryption & Identity

Enforces TLS in transit via MTA-STS policy files and renders verified trademarked SVG Tiny PS brand logos under VMC certificates in Gmail, Yahoo, and Apple Mail inboxes.

Practical Use Cases & Diagnostic Scenarios

Common administrative and operational scenarios solved by this tool

01Bulk Sender Compliance Verification

Audit sending domains against Google and Yahoo's mandatory bulk sender requirements. Confirm that your domain publishes valid SPF and DKIM records, maintains strict DMARC alignment, and prevents rejection when delivering to over 5,000 daily consumer recipients.

02Diagnosing SPF Permerror & Lookup Limits

Identify when combining multiple SaaS providers (Google Workspace, Zendesk, Mailchimp, Salesforce) causes your SPF record to exceed RFC 7208's strict 10-lookup threshold, triggering permanent authentication failures at receiving mail gateways.

03Executive Impersonation & Spoofing Defense

Verify whether your domain allows bad actors to forge your sender address in phishing campaigns. Test whether your DMARC policy enforces quarantine or reject, stopping business email compromise (BEC) and unauthorized outbound spoofing.

04Third-Party ESP Delegation & Selector Auditing

Confirm that automated marketing platforms and transactional gateways (SendGrid, Postmark, Amazon SES) have published valid 2048-bit DKIM keys at their assigned selector records before initiating outbound marketing or password-reset campaigns.