Sender Policy Framework
Without a correct SPF record, your domain's email will fail or be deferred by major receivers (Gmail, Outlook). Set correctly as part of basic email deliverability.
What It Defines
Defines SPF DNS TXT records that publish which mail servers are authorized to send email on behalf of a domain. Receiving MTAs check SPF to detect forged From addresses.
Canonical (Normative)
Convenient (Practical)
The canonical publication point for finalized RFCs. If a protocol is standardized as an RFC, the RFC Editor text is the normative final reference. Published by the IETF, IRTF, IAB, and independent stream.
Related Specs
DKIM is required to pass DMARC. Without it, your email won't be trusted by major providers. Set up alongside SPF as part of any serious email configuration.
DMARC is the final layer of email authentication. Without it, your domain can be spoofed in phishing. Google and Yahoo require DMARC for bulk senders.
The record types (A, MX, TXT, CNAME) you configure in every DNS panel live in this spec. Know what you're setting.