Email RFC Reference

RFC 1869 RFC 1869 – SMTP Service Extensions (ESMTP) RFC 2920 RFC 2920 – SMTP Pipelining RFC 3030 RFC 3030 – SMTP BINARYMIME and CHUNKING RFC 5321 RFC 5321 – Simple Mail Transfer Protocol RFC 5322 RFC 5322 – Internet Message Format RFC 5598 RFC 5598 – Internet Mail Architecture RFC 6409 RFC 6409 – Message Submission for Mail RFC 6531 RFC 6531 – SMTP Extension for Internationalized Email RFC 6532 RFC 6532 – Internationalized Email Headers

RFC 4954 RFC 4954: SMTP AUTH Extension RFC 5617 Author Domain Signing Practices RFC 8463 RFC 8463: Ed25519 for DKIM Signatures RFC 8601 Authentication-Results Header Field RFC 6376 DomainKeys Identified Mail RFC 8617 Authenticated Received Chain RFC 7489 Domain-based Message Authentication, Reporting and Conformance RFC 7208 Sender Policy Framework

RFC 3207 RFC 3207 – SMTP STARTTLS Extension RFC 7817 RFC 7817: Updated TLS Server Identity Check for Email RFC 8314 RFC 8314: Cleartext Considered Obsolete RFC 8689 RFC 8689: SMTP Require TLS Option RFC 8461 Mail Transfer Agent Strict Transport Security RFC 7672 DNS-Based Authentication for SMTP TLS

RFC 2045 Format of Internet Message Bodies RFC 2046 Media Types RFC 2047 Message Header Extensions for Non-ASCII Text RFC 2049 Conformance Criteria and Examples RFC 2231 RFC 2231: MIME Parameter Value Extensions

RFC 3461 RFC 3461: SMTP Delivery Status Notification Extension RFC 3462 RFC 3462: Multipart/Report Content Type RFC 3463 RFC 3463: Enhanced Mail System Status Codes RFC 3464 RFC 3464: Delivery Status Notification Format RFC 5248 RFC 5248: SMTP Enhanced Status Codes Registry RFC 6522 RFC 6522: Multipart/Report Media Type (Updated)

RFC 5965 Abuse Reporting Format RFC 6591 RFC 6591: Authentication Failure Reporting (AFRF) RFC 6652 RFC 6652: SPF Authentication Failure Reporting RFC 8460 RFC 8460: SMTP TLS Reporting (TLSRPT)

RFC 2369 RFC 2369: List-Unsubscribe and List-* Headers RFC 3834 RFC 3834: Automatic Responses in Email RFC 6377 RFC 6377: DKIM and Mailing Lists RFC 6854 RFC 6854: Group Syntax in From and Sender Header Fields RFC 8058 RFC 8058: One-Click Unsubscribe for Email

RFC 1035 RFC 1035 – Domain Names: Implementation and Specification RFC 5782 RFC 5782: DNS-Based Blacklists and Whitelists RFC 6186 RFC 6186: SRV Records for Email Service Autodiscovery RFC 7505 No Service for Domain

RFC 1939 Post Office Protocol Version 3 RFC 8620 JSON Meta Application Protocol RFC 9051 RFC 9051: IMAP4rev2

RFC 5751 RFC 5751: S/MIME 3.2 Message Specification RFC 8551 RFC 8551: S/MIME 4.0 Message Specification

Guide The Complete Email Deliverability Guide Guide TLS and Email Security Guide IP and Domain Reputation Guide DNS and Mail Routing Guide The Lifecycle of an Email Guide How SMTP Really Works Guide Understanding Email Bounces Guide How Spam Filters Work Guide Email Authentication Explained Guide Anatomy of Email Headers