Email authentication
Check SPF
Check SPF syntax, mechanisms, dependencies, DNS lookup limits and network ranges.
Enter only the domain, such as example.com – without https://, a path or an email address.
A new check is available every 5 minutes per tool and domain. Until then, you see the saved result.
What the tool accesses
DNS.
How the check works
What exactly is checked?
- Find the SPF TXT record and check for missing, duplicate or invalid policies.
- Evaluate mechanisms, qualifiers, modifiers, CIDR networks and the final all policy.
- Recursively resolve statically discoverable include and redirect dependencies.
- Evaluate DNS lookups, queries without matching records, loops, recursion depth and unusually broad networks.
Assessment
How is the result determined?
Passed means there is exactly one usable SPF record, no loop or invalid reference, DNS limits are respected, and the policy does not authorize every sender indiscriminately.
- Checker
3.0.0- What the tool accesses
- DNS
- Technical standards and sources
- RFC 7208
A technical snapshot, not a certificate or a delivery guarantee. Methodology public-tools-v1. Reviewed on 20.08.2026.