SPF check

Validate your SPF record's syntax, walk include chains, and count DNS lookups against the RFC 7208 limit of 10.

Related tools

DMARC check

Policy and alignment

Blacklist check

Spamhaus, SORBS, more

DNS lookup

A, AAAA, MX, TXT, NS

About SPF

SPF (Sender Policy Framework) is a TXT record that lists which mail servers are allowed to send email on behalf of your domain. When a receiving server gets a message claiming to be from you@example.com, it checks your SPF record to verify the sending IP is authorized.

The most common failure mode is too many DNS lookups. RFC 7208 limits SPF evaluation to 10 DNS queries — once you exceed it, recipients are required to return PermError, which usually means rejection. Each include: adds at least one lookup (sometimes more, if the included record itself has includes). Google Workspace alone uses 4. Microsoft 365 uses 3. Stack a couple of third-party senders on top and you're over the limit.

Healthy SPF records end in -all (strict) or ~all (softfail). +all means "anyone can send as me" and is almost always a misconfiguration.