RFC 7505: A Null MX No Service Resource Record for Domains That Accept No Mail
Defines the Null MX (0 .) record that explicitly signals a domain accepts no incoming mail, preventing delivery loops.
DNS records
SPF Records Explained: Syntax, Examples and Common Mistakes (2026)
SPF is the TXT record that tells receiving mail servers which IPs are authorized to send email for your domain. This guide covers syntax, real-world examples by provider (Google, Microsoft, SendGrid, ...
DKIM Record Explained: Syntax, Setup and Common Mistakes (2026)
DKIM is the cryptographic signature that proves your email was not altered in transit. This guide covers selectors, tag syntax, real setup steps for Google Workspace, Microsoft 365, SendGrid, ...
DMARC Record Explained: Policy, Reports and Roll-Out Roadmap (2026)
DMARC is the policy that tells receivers what to do when SPF or DKIM fail. This guide covers syntax, tag reference, the three policies (none, quarantine, reject), alignment, reading aggregate ...
