SPF Records Explained: How to Prevent Email Spoofing

Sender Policy Framework (SPF) is an email authentication method that specifies which mail servers are authorized to send email on behalf of your domain.

How SPF Works

When an email is received, the receiving server checks the SPF record published in your domain's DNS. The record lists approved IP addresses and mail servers that can send email for your domain.

SPF Record Syntax

A typical SPF record looks like this:

``` v=spf1 ip4:192.0.2.0/24 include:_spf.google.com ~all ```

SPF Mechanisms

**v=spf1**: Version identifier
**ip4/ip6**: Authorize specific IP addresses
**include**: Include another domain's SPF policy
**all**: Default action (- = fail, ~ = softfail, ? = neutral)

Common SPF Mistakes

1. **Too Many DNS Lookups**: SPF has a 10 DNS lookup limit 2. **Multiple SPF Records**: Only one SPF record per domain 3. **Missing Include Statements**: Forgetting email service providers

Best Practices

Start with ~all (softfail) and monitor
Use IP ranges instead of individual IPs when possible
Regularly audit your SPF record
Consider SPF flattening for complex setups