SPF (Sender Policy Framework)
Summary
SPF is an email authentication standard that specifies which mail servers are authorized to send email for your domain. SPF records are published as DNS TXT records and validated by receiving mail servers. Without SPF, anyone can forge emails claiming to be from your domain.
What Is SPF (Sender Policy Framework)?
SPF (Sender Policy Framework) is a DNS-based email authentication mechanism defined in RFC 7208. It allows domain owners to publish a list of authorized mail servers in a TXT record at the root domain. When a receiving mail server gets an email claiming to be from your domain, it checks the SPF record to verify the sending server is authorized. This prevents email spoofing and phishing attacks.
Why SPF (Sender Policy Framework) Matters for Email & DNS Security
SPF is the foundation of email authentication. Without it, anyone can send emails claiming to be from your domain, your legitimate emails may be marked as spam, DMARC policies cannot be enforced, and your domain reputation suffers from forgeries. According to IntoDNS.ai data, 34% of domains exceed the 10 DNS lookup limit, causing SPF validation failures. Major email providers (Gmail, Outlook, Yahoo) require SPF for reliable inbox delivery.
How SPF (Sender Policy Framework) Works (Technical)
- 1.Domain owner publishes SPF record as DNS TXT record
- 2.Sending mail server sends email with envelope sender (MAIL FROM)
- 3.Receiving server extracts domain from envelope sender
- 4.Receiving server queries DNS for SPF record
- 5.SPF record evaluated: mechanisms checked in order (ip4, ip6, include, a, mx)
- 6.Result: pass, fail, softfail, neutral, temperror, or permerror
- 7.Result combined with DMARC for final delivery decision
Common Misconfigurations
❌ Multiple SPF records
Consequence: SPF validation fails (RFC violation - only one TXT record allowed)
How IntoDNS detects this: IntoDNS checks for duplicate TXT records starting with v=spf1
❌ Exceeding 10 DNS lookup limit
Consequence: SPF validation returns permerror, email may be rejected. According to IntoDNS analysis, exceeding the lookup limit is the most common SPF misconfiguration, affecting 34% of domains with SPF.
How IntoDNS detects this: IntoDNS recursively resolves all include: mechanisms and counts lookups
❌ Using +all or ?all
Consequence: Allows anyone to send email (defeats purpose of SPF)
How IntoDNS detects this: IntoDNS flags permissive qualifiers as critical security issue
How IntoDNS.ai Detects & Scores This
IntoDNS validates SPF through existence check, syntax validation (RFC 7208), DNS lookup counting (≤10), qualifier assessment (-all vs ~all), include resolution, and IP range validation. SPF accounts for 15% of email security score.
How To Fix SPF (Sender Policy Framework) Issues
- 1.Log into your DNS provider
- 2.Create TXT record at root domain (@)
- 3.Start with: v=spf1 ~all
- 4.Add authorized senders: include:_spf.google.com
- 5.Add IPs: ip4:203.0.113.1
- 6.Verify with IntoDNS (lookup count ≤10)
- 7.Change ~all to -all after testing
References
Source: IntoDNS.ai – DNS & email security diagnostics
Last updated: 2026-01-14
Category: email