Spamhaus ZEN: Email Blocklist Removal Guide
Composite zone combining SBL (spam sources), XBL (exploited IPs), and PBL (policy block list) into a single DNSBL query. The most widely deployed IP blocklist in the world. A listing…
email security
RFC 4409: Message Submission for Mail
Earlier version of the submission RFC. Obsoleted by RFC 6409.
RFC 6647: Email Greylisting: An Applicability Statement for SMTP
Formalises the greylisting technique where MTAs temporarily reject unknown senders to filter out botnet spam.
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.
RFC 5518: Vouch By Reference (VBR)
Defines a third-party endorsement mechanism where a trusted voucher certifies a sender's reputation via DNS.
RFC 5863: DomainKeys Identified Mail (DKIM) Development, Deployment, and Operations
Operational guide for deploying DKIM: key rotation, selector management, DNS setup, and troubleshooting.
RFC 1847: Security Multiparts for MIME: Multipart/Signed and Multipart/Encrypted
Defines MIME framework for signed and encrypted message parts, foundation for S/MIME and PGP/MIME.
RFC 5751: Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.2
Defines S/MIME 3.2 for signing and encrypting email using X.509 certificates.
RFC 2449: POP3 Extension Mechanism
Defines the CAPA command that lets POP3 clients discover server capabilities.
RFC 1734: POP3 Authentication Command
Defines the AUTH command for POP3, enabling SASL-based authentication methods beyond USER/PASS.
