7293 The Require-Recipient-Valid-Since Header Field and SMTP Service Extension
7372 Email Authentication Status Codes
7435 Opportunistic Security: Some Protection Most of the Time
7504 SMTP 521 and 556 Reply Codes
7505 A "Null MX" No Service Resource Record for Domains That Accept No Mail
8098 Message Disposition Notification
8601 Message Header Field for Indicating Message Authentication Status
8689 SMTP Require TLS Option
# SPF
4408 (obsoleted by RFC 7208) Sender Policy Framework (SPF) for Authorizing Use of Domains in E-Mail, Version 1
6652 Sender Policy Framework (SPF) Authentication Failure Reporting Using the Abuse Reporting Format
7208 Sender Policy Framework (SPF) for Authorizing Use of Domains in Email, Version 1
7208-eid5436 errata: header-field FWS
7208-eid6721 errata: corrected smtp example response
7208-eid4751 errata (not verified): ptr mechanism
7208-eid5227 errata (not verified): ptr lookup order
7208-eid6595 errata (not verified): 2 void lookups vs exists
7208-eid6216 errata (not verified): ptr in multiple requirements example from appendix A.4
# DKIM
6376 DomainKeys Identified Mail (DKIM) Signatures
6376-eid4810 errata: q= qp-hdr-value
6376-eid5070 errata: tag-spec
4686 Analysis of Threats Motivating DomainKeys Identified Mail (DKIM)
4871 (obsoleted by RFC 6376) DomainKeys Identified Mail (DKIM) Signatures
5016 Requirements for a DomainKeys Identified Mail (DKIM) Signing Practices Protocol
5585 DomainKeys Identified Mail (DKIM) Service Overview
5672 (obsoleted by RFC 6376) DomainKeys Identified Mail (DKIM) Signatures -- Update
5863 DomainKeys Identified Mail (DKIM) Development, Deployment, and Operations
6377 DomainKeys Identified Mail (DKIM) and Mailing Lists
8032 Edwards-Curve Digital Signature Algorithm (EdDSA)
8301 Cryptographic Algorithm and Key Usage Update to DomainKeys Identified Mail (DKIM)
8463 A New Cryptographic Signature Method for DomainKeys Identified Mail (DKIM)
# DMARC
7489 Domain-based Message Authentication, Reporting, and Conformance (DMARC)
7489-eid5440 errata: valid dmarc records with(out) semicolon
7489-eid6729 errata (not verified): publicsuffix list only for ICANN DOMAINS
7960 Interoperability Issues between Domain-based Message Authentication, Reporting, and Conformance (DMARC) and Indirect Email Flows
9091 Experimental Domain-Based Message Authentication, Reporting, and Conformance (DMARC) Extension for Public Suffix Domains
# DKIM/SPF/DMARC
8616 Email Authentication for Internationalized Mail
# Greylisting
6647 Email Greylisting: An Applicability Statement for SMTP
# DNSBL/DNSWL
5782 DNS Blacklists and Whitelists
8904 DNS Whitelist (DNSWL) Email Authentication Method Extension
# DANE
6698 The DNS-Based Authentication of Named Entities (DANE) Transport Layer Security (TLS) Protocol: TLSA
7218 Adding Acronyms to Simplify Conversations about DNS-Based Authentication of Named Entities (DANE)
7671 The DNS-Based Authentication of Named Entities (DANE) Protocol: Updates and Operational Guidance
7672 SMTP Security via Opportunistic DNS-Based Authentication of Named Entities (DANE) Transport Layer Security (TLS)
# TLS-RPT
8460 SMTP TLS Reporting
8460-eid6241 Wrong example for JSON field "mx-host".
# MTA-STS
8461 SMTP MTA Strict Transport Security (MTA-STS)
# ARC
8617 The Authenticated Received Chain (ARC) Protocol
# ARF
5965 An Extensible Format for Email Feedback Reports
6650 Creation and Use of Email Feedback Reports: An Applicability Statement for the Abuse Reporting Format (ARF)
6591 Authentication Failure Reporting Using the Abuse Reporting Format
6692 Source Ports in Abuse Reporting Format (ARF) Reports
# IMAP
1730 (obsoleted by RFC 2060) INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4
2060 (obsoleted by RFC 3501) INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1
3501 (obsoleted by RFC 9051) INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1
9051 Internet Message Access Protocol (IMAP) - Version 4rev2
1733 DISTRIBUTED ELECTRONIC MAIL MODELS IN IMAP4
2087 IMAP4 QUOTA extension
2088 (obsoleted by RFC 7888) IMAP4 non-synchronizing literals
2152 UTF-7 A Mail-Safe Transformation Format of Unicode
2177 IMAP4 IDLE command
2180 IMAP4 Multi-Accessed Mailbox Practice
2193 IMAP4 Mailbox Referrals
2342 IMAP4 Namespace
2683 IMAP4 Implementation Recommendations
2971 IMAP4 ID extension
3348 (obsoleted by RFC 5258) The Internet Message Action Protocol (IMAP4) Child Mailbox Extension
3502 Internet Message Access Protocol (IMAP) - MULTIAPPEND Extension
3503 Message Disposition Notification (MDN) profile for Internet Message Access Protocol (IMAP)
3516 IMAP4 Binary Content Extension
3691 Internet Message Access Protocol (IMAP) UNSELECT command
4314 IMAP4 Access Control List (ACL) Extension
4315 Internet Message Access Protocol (IMAP) - UIDPLUS extension
4466 Collected Extensions to IMAP4 ABNF
4467 Internet Message Access Protocol (IMAP) - URLAUTH Extension
4469 Internet Message Access Protocol (IMAP) CATENATE Extension
4549 Synchronization Operations for Disconnected IMAP4 Clients
4550 (obsoleted by RFC 5550) Internet Email to Support Diverse Service Environments (Lemonade) Profile
4551 (obsoleted by RFC 7162) IMAP Extension for Conditional STORE Operation or Quick Flag Changes Resynchronization
4731 IMAP4 Extension to SEARCH Command for Controlling What Kind of Information Is Returned
4978 The IMAP COMPRESS Extension
4959 IMAP Extension for Simple Authentication and Security Layer (SASL) Initial Client Response
5032 WITHIN Search Extension to the IMAP Protocol
5092 IMAP URL Scheme
5161 The IMAP ENABLE Extension
5162 (obsoleted by RFC 7162) IMAP4 Extensions for Quick Mailbox Resynchronization
5182 IMAP Extension for Referencing the Last SEARCH Result
5255 Internet Message Access Protocol Internationalization
5256 Internet Message Access Protocol - SORT and THREAD Extensions
5257 Internet Message Access Protocol - ANNOTATE Extension
5258 Internet Message Access Protocol version 4 - LIST Command Extensions
5259 Internet Message Access Protocol - CONVERT Extension
5267 Contexts for IMAP4
5464 The IMAP METADATA Extension
5465 The IMAP NOTIFY Extension
5466 IMAP4 Extension for Named Searches (Filters)
5530 IMAP Response Codes
5550 The Internet Email to Support Diverse Service Environments (Lemonade) Profile
5738 (obsoleted by RFC 6855) IMAP Support for UTF-8
5788 IMAP4 Keyword Registry
5819 IMAP4 Extension for Returning STATUS Information in Extended LIST
5957 Display-Based Address Sorting for the IMAP4 SORT Extension
6154 IMAP LIST Extension for Special-Use Mailboxes
6203 IMAP4 Extension for Fuzzy Search
6237 (obsoleted by RFC 7377) IMAP4 Multimailbox SEARCH Extension
6851 Internet Message Access Protocol (IMAP) - MOVE Extension
6855 IMAP Support for UTF-8
6858 Simplified POP and IMAP Downgrading for Internationalized Email
7162 IMAP Extensions: Quick Flag Changes Resynchronization (CONDSTORE) and Quick Mailbox Resynchronization (QRESYNC)
7377 IMAP4 Multimailbox SEARCH Extension
7888 IMAP4 Non-synchronizing Literals
7889 The IMAP APPENDLIMIT Extension
8437 IMAP UNAUTHENTICATE Extension for Connection Reuse
8474 IMAP Extension for Object Identifiers
8438 IMAP Extension for STATUS=SIZE
8457 IMAP "$Important" Keyword and "\Important" Special-Use Attribute
8508 IMAP REPLACE Extension
8514 Internet Message Access Protocol (IMAP) - SAVEDATE Extension
8970 IMAP4 Extension: Message Preview Generation
5198 Unicode Format for Network Interchange
# Mailing list
2369 The Use of URLs as Meta-Syntax for Core Mail List Commands and their Transport through Message Header Fields
2919 List-Id: A Structured Field and Namespace for the Identification of Mailing Lists
# Sieve
5228 Sieve: An Email Filtering Language
and many more, see http://sieve.info/documents
# Vouch by reference
5518 Vouch By Reference
# TLS
6125 Representation and Verification of Domain-Based Application Service Identity within Internet Public Key Infrastructure Using X.509 (PKIX) Certificates in the Context of Transport Layer Security (TLS)
7525 Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)
8314 Cleartext Considered Obsolete: Use of Transport Layer Security (TLS) for Email Submission and Access
8996 Deprecating TLS 1.0 and TLS 1.1
8997 Deprecation of TLS 1.1 for Email Submission and Access