SPF Basics

Foundational guides to understanding Sender Policy Framework.

How SPF Works: The Complete Authentication Flow Explained

Understand how SPF email authentication works, from DNS lookups to pass/fail results. Learn about mechanisms, qualifiers, and more.

The SPF "a" Mechanism Explained

Learn how the SPF "a" mechanism works, when to use it, its syntax with and without a domain argument, and how it compares to the "mx" mechanism.

SPF "all" Mechanism: Softfail vs Hardfail Explained

Understand the SPF all mechanism and its qualifiers: +all, -all, ~all, and ?all. Learn the difference between softfail and hardfail.

SPF Exists Mechanism: What It Does and When You Need It

Learn what the SPF exists mechanism does, how it uses macros and DNS A records for IP authorization, and when to use exists vs include in your SPF record.

SPF FAQ: Frequently Asked Questions About SPF Records

Answers to common SPF questions: multiple records, propagation time, DNS lookups, combining includes, and more. Get your SPF questions answered.

SPF Include Mechanism: How It Works and When to Use It

Learn how the SPF include mechanism works, how to use multiple includes in one record, and how each include affects your DNS lookup count.

SPF ip4 and ip6 Mechanisms: Authorizing IP Addresses

Learn how to use SPF ip4 and ip6 mechanisms to authorize IP addresses. Covers syntax, CIDR ranges, IP vs include, and common mistakes.

SPF Macros Explained: Dynamic Variables in SPF Records

Learn what SPF macros are, what each variable does, and when they're useful. A plain-English guide to SPF record macros.

SPF Record Examples: Real-World Records for Every Scenario

Practical SPF record examples for common setups including Google Workspace, Microsoft 365, SendGrid, and multi-provider configurations.

SPF Redirect vs Include: When to Use the Redirect Modifier

Learn the difference between SPF redirect and include. Know when to use the redirect modifier to centralize SPF across domains.

SPF Softfail vs Hardfail: Which Should You Use?

Understand the difference between SPF softfail (~all) and hardfail (-all), how receiving servers treat each, and which one is right for your domain.

SPF Record Syntax: A Complete Reference Guide

Learn every SPF record syntax element including mechanisms, qualifiers, and modifiers. A plain-English guide with examples.

What is SPF? A Plain-English Guide

Learn what SPF (Sender Policy Framework) is, why it matters for email deliverability, and how it helps prevent email spoofing. No technical jargon required.