Free Raw SPF Syntax Checker & Offline RFC 7208 Inspector
Paste the SPF record you’re about to publish and catch mistakes before they hit DNS. This offline validator parses every mechanism, flags unknown terms and qualifiers, estimates the DNS-lookup cost of your structure, and marks anything that would trigger a PermError — all without touching live DNS.
Raw SPF Record Syntax & Limit Validator
Paste any raw SPF TXT record string to validate syntax correctness, mechanisms (`include`, `ip4`, `ip6`, `a`, `mx`, `redirect`), qualifier safety (`~all` vs `-all`), and calculate lookup overhead before touching live DNS.
Tool Overview: What It Does & Core Purpose
The **AutoSMTP Raw SPF Checker** acts as an offline, pre-flight compiler and syntax linter for Sender Policy Framework records. Before publishing changes to live DNS nameservers—where propagation delays can take hours and syntax mistakes cause immediate delivery failure across receiving mailboxes—engineers can test their draft strings. The tool validates RFC 7208 mechanism structure, qualifier security, CIDR notation, and calculates exact DNS lookup overhead.Key Advantages & Architectural Benefits
Advantage
**Zero-DNS Pre-Flight Linting:** Verify raw SPF strings locally before modifying production DNS zone files.
Advantage
**RFC 7208 Lookup Counter:** Flags whether your includes, redirects, and A/MX mechanisms exceed the strict 10-lookup barrier.
Advantage
**Qualifier Security Inspection:** Alerts administrators to dangerous directives like `+all` that expose domains to spoofing.
Advantage
**Instant Client-Side Feedback:** Executes instantly with zero server latency or network propagation wait time.
Email Marketing & Cold Outreach Integration
How This Tool Accelerates Email Campaigns & Deliverability
A single syntax typo in an SPF record causes receiving MTAs to declare a `PermError` (Permanent Error), which modern anti-spam filters treat as an authentication failure. Pre-validating raw strings through the AutoSMTP SPF Raw Checker prevents accidental delivery blackouts during infrastructure migrations.Frequently Asked Questions (FAQs)
Why does RFC 7208 limit DNS lookups to 10? ▾
The 10-lookup ceiling was established to prevent Denial-of-Service (DoS) amplification attacks against DNS servers. If an SPF record requires more than 10 DNS queries, RFC 7208 mandates that receivers abort evaluation and return a `PermError`.
What is the difference between ~all and -all? ▾
`~all` represents a SoftFail, instructing receivers to accept the message but apply additional heuristic scrutiny. `-all` represents a HardFail, instructing receivers to reject the message outright. In modern DMARC environments, `~all` is recommended.
Do ip4 and ip6 mechanisms count toward the 10-lookup limit? ▾
No! Direct IP mechanisms (`ip4:192.0.2.1/24`, `ip6:…`) do not require any DNS resolution and incur zero lookup cost. Flattening includes into direct IP ranges is how AutoSMTP bypasses the 10-lookup ceiling.
Can I have more than one SPF TXT record for my domain? ▾
NO! Under RFC 7208 Section 3.2, a domain must NEVER have more than one SPF record. Publishing multiple SPF records causes an immediate `PermError`.
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Key capabilities
- Full mechanism/qualifier parsing
- Lookup-cost estimate per mechanism
- PermError and deprecated-syntax warnings
- Works on records still in draft or change tickets.
Anatomy of an SPF record
Every SPF TXT record starts with the version tag v=spf1 — lowercase, exact, and required; anything else and receivers treat the record as absent. What follows is a sequence of mechanisms evaluated strictly left to right, first match wins: all, include:, a, mx, ptr, ip4:, ip6: and exists:. Each can carry a qualifier: + pass (the default), - fail, ~ softfail, ? neutral. Two modifiers — redirect= and exp= — redirect evaluation to another record or supply an explanation string.
If no mechanism matches, evaluation falls through to an implicit neutral result — which is why a record without an all term or a redirect= gives receivers no instruction at all. End with ~all while warming, -all once DMARC reports confirm no false positives. Exactly one SPF record per domain — two is an automatic PermError.
Frequently asked questions
What’s the difference between this and the live SPF checker?
This validates the record’s syntax and structure offline — perfect for pre-publish review. The live checker resolves your actual DNS and follows the include chain. Use both: draft here, verify live.
Why is the 10-lookup estimate important?
Each include/a/mx/exists mechanism forces receivers to perform a DNS query. Exceed 10 and receivers return PermError regardless of your syntax.