Complete SPF Guide
SPF: Everything You Need To Know
Guides, tools, and resources to master Sender Policy Framework — organized from first principles to staying under the 10-lookup limit for good.
30 hand-picked guides, tools & resources
SPF Fundamentals
Start here if you're new to SPF. Learn what Sender Policy Framework does, how a record is structured, and the mechanisms that decide which servers may send mail for your domain — the groundwork everything else builds on.
What is SPF?
Understand Sender Policy Framework — how it authorizes sending servers and forms the first pillar of email authentication.
SPF Record Format
The anatomy of an SPF TXT record: version, mechanisms, qualifiers, and the all mechanism that closes every record.
SPF Mechanisms Explained
What a, mx, ip4, ip6, and include actually do — and how each one contributes to (and counts against) your record.
Understanding SPF Syntax
A close read of SPF syntax so you can write, edit, and debug records with confidence instead of copy-paste guesswork.
SPF Glossary
Every SPF term in one place — mechanisms, qualifiers, PermError/TempError, and the jargon that shows up in reports.
Create & Configure
Ready to publish? These step-by-step guides walk through building a valid SPF record and adding it at the providers most teams use — Microsoft 365, Google Workspace, and Cloudflare — without breaking existing mail flow.
How to Create an SPF Record
A practical walkthrough to build your first SPF record and publish it as a DNS TXT entry the right way.
SPF Record Examples
Real, annotated SPF records you can learn from and adapt — from a single sender to a multi-provider setup.
Office 365 SPF Setup
Publish an SPF record for Microsoft 365 that authorizes Exchange Online without knocking out your other senders.
Google Workspace SPF Setup
The correct include for Google Workspace and how to combine it with other sources in a single valid record.
Add an SPF Record in Cloudflare
Click-by-click guide to publishing your SPF TXT record in Cloudflare DNS and verifying it resolves correctly.
The 10-Lookup Limit & Flattening
The most common way SPF silently breaks: too many DNS lookups. RFC 7208 caps evaluation at 10 lookups, and busy records blow past it. Learn why it happens, what flattening really does, and how a dedicated service keeps you under the limit for good.
SPF Too Many DNS Lookups
Why the 10-lookup limit triggers a PermError, how to diagnose it, and the ways to bring your record back under budget.
SPF Checker
Check any domain live — see the full include tree, count your DNS lookups, and spot exactly what pushes you over 10.
What is SPF Flattening?
How flattening resolves nested includes into IP addresses to collapse your lookup count — and the trade-offs to know.
SPF Flattening Myths
Separating fact from fiction on flattening — what it does, what it does not, and when it is the right call.
Combine SPF Records Correctly
You can only have one SPF record per domain — here is how to merge multiple senders into it without errors.
Why a Dedicated SPF Service
Why automated, hosted SPF flattening beats manual fixes — records that stay valid as your senders change.
Errors & Troubleshooting
SPF is set up but mail still fails? These guides help you read the error, find the sending source, and fix the record — the fixes teams reach for most after go-live, plus a validator to confirm you're clean.
Fix SPF PermError & TempError
What each error means and a DIY path to resolve them — from lookup limits to malformed syntax and DNS timeouts.
SPF Validation Failed
Why an SPF check fails, what receivers do about it, and a step-by-step method to track down the root cause.
SPF Validator
Validate your record syntax and mechanisms instantly, and confirm it evaluates cleanly before you rely on it.
Advanced SPF Record Testing
Go beyond a pass/fail check — testing techniques that catch PermError risks before receivers do.
Eliminate PermError & Lookup Issues
Validation tips that target the two failure modes that break enterprise records: lookup overflow and bad syntax.
Advanced SPF
Take your setup further. Explore SPF macros, the macros-versus-flattening trade-off, the case for regular record checks, and where SPF is headed — the topics that round out a genuinely hardened configuration.
SPF Macros vs Flattening
Two very different techniques compared — when macros make sense, when flattening wins, and why they are not interchangeable.
SPF Macros Explained
What SPF macros are, the syntax that drives them, and the narrow set of cases where they earn their complexity.
The Complete SPF Record Guide
A single deep-dive across syntax, lookups, flattening, and testing — the long-form reference to keep bookmarked.
10 Reasons to Check SPF Regularly
Records drift as senders change. Here is why routine SPF checks belong in your security hygiene, not just setup.
The Future of SPF
Where email authentication is heading and how SPF fits alongside DKIM, DMARC, and the standards coming next.
Free SPF Tools
No account, no sign-up — check, generate, validate, and look up SPF records in seconds. Every tool links to the canonical version so you always land on the same trusted page.
SPF Checker
Check a domain live, expand the full include tree, and count DNS lookups against the 10-lookup limit.
SPF Record Generator
Build a valid SPF record for your senders in seconds — correct syntax, no guesswork.
SPF Validator
Validate record syntax and mechanisms and confirm the record evaluates cleanly.
SPF Record Lookup
Look up the published SPF record for any domain and read it back in plain terms.
Stop fighting the 10-lookup limit.
AutoSPF flattens your record automatically and keeps it valid as your senders change — so SPF just works, permanently. Set it once and forget PermErrors.
Trusted by 50,000+ domains
"AutoSPF Flattens SPF Records Seamlessly & Keeps Changes Logged - I am quite pleased with the product"
It does what it promises to do, and does it very well. I appreciate that it keeps a log of changes made, which prevents many mistakes. A client's SPF record would have way too many lookups, but AutoSPF makes that problem go away. The length of the SPF record is typically not the issue; it's the amount of lookups in the record that are. AutoSPF "flattens" the record, automatically expanding the defined lookups to IP addresses or ranges. And it auto-updates the record when the un-flattened lookups change.
Peter J.
President · Small-Business (50 or fewer emp.)
"Helped us go beyond capacity"
AutoSPF did exactly as described, it helped us get past our 10 lookup limit. Afterwards, we hit another limit regarding overall capacity and when contacted, they quickly provided us with a new solution to eliminate capacity issues entirely going forward, so now we can add as many SPF records as needed. They also provided us with a personalized support video explaining their new method in its entirety using our instance as the example.
Verified User
Financial Services · Mid-Market (51-1000 emp.)
"Great service and great support"
AutoSPF was easy to initially set up on our own and a great cost effective entry into spf flattening. Needed our first support assistance today and got great response including a video demonstrating the issue I was trying to solve, a quick fix, and more detailed followup.
Greg F.
Mid-Market (51-1000 emp.)