RFC & standards compatibility
This list presents the most notable standards and RFC that Halon has implemented in regards to SMTP and MIME, and which we aim to support when applicable in order to achieve maximum interopability and compliancy.
| Link | Short name | Long name | Introduced | Halon Version |
|---|---|---|---|---|
| rfc1870 | SIZE | SMTP Service Extension for Message Size Declaration | 2020 | 5.4 (2.0) |
| rfc2033 | LMTP | Local Mail Transfer Protocol | 2014 | 3.2.9 |
| rfc2034 | ENHANCEDSTATUSCODES | SMTP Service Extension for Returning Enhanced Error Codes | 2008 | 2.0 |
| rfc2045 | MIME | Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies | 2008 | 2.0 |
| rfc2046 | MIME | Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types | 2008 | 2.0 |
| rfc2047 | MIME | MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text | 2008 | 2.0 |
| rfc2183 | MIME | Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field | 2008 | 2.0 |
| rfc2231 | MIME | MIME Parameter Value and Encoded Word Extensions: Character Sets, Languages, and Continuations | 2008 | 2.0 |
| rfc2920 | PIPELINING | SMTP Service Extension for Command Pipelining | 2008 | 2.0 |
| rfc3030 | CHUNKING | SMTP Service Extensions for Transmission of Large and Binary MIME Messages | 2020 | 5.4 |
| rfc3207 | STARTTLS | SMTP Service Extension for Secure SMTP over Transport Layer Security | 2008 | 2.0 |
| rfc3461 | DSN | Simple Mail Transfer Protocol (SMTP) Service Extension for Delivery Status Notifications (DSNs) | 2008 | 2.0 |
| rfc3463 | Enhanced Mail System Status Codes | 2008 | 2.0 | |
| rfc3464 | DSN | An Extensible Message Format for Delivery Status Notifications | 2008 | 2.0 |
| rfc3848 | ESMTP and LMTP Transmission Types Registration | 2008 | 2.0 | |
| rfc4954 | AUTH | SMTP Service Extension for Authentication | 2008 | 2.0 |
| rfc5321 | SMTP | Simple Mail Transfer Protocol | 2008 | 2.0 |
| rfc5322 | Internet Message Format | 2008 | 2.0 | |
| rfc5782 | DNSBL | DNS Blacklists and Whitelists | 2011 | 2.2 |
| rfc5965 | ARF | An Extensible Format for Email Feedback Reports | 2021 | n/a |
| rfc6152 | 8BITMIME | SMTP Service Extension for 8-bit MIME Transport | 2008 | 2.0 |
| rfc6376 | DKIM | DomainKeys Identified Mail (DKIM) Signatures | 2010 | 2.2 |
| rfc6409 | Message Submission for Mail | 2008 | 2.0 | |
| rfc6522 | DSN | The Multipart/Report Media Type for the Reporting of Mail System Administrative Messages | 2008 | 2.0 |
| rfc6531 | SMTPUTF8 | SMTP Extension for SMTPUTF8 | 2017 | 4.0 |
| rfc6532 | Internationalized Email Headers | 2008 | 2.0 | |
| rfc6533 | DSN | Internationalized Delivery Status and Disposition Notifications | 2008 | 2.0 |
| rfc6698 | DANE | The DNS-Based Authentication of Named Entities (DANE) Transport Layer Security (TLS) Protocol: TLSA | 2015 | 3.4.2 |
| rfc7208 | SPF | Sender Policy Framework (SPF) for Authorizing Use of Domains in Email, Version 1 | 2008 | 2.0 |
| rfc7489 | DMARC | Domain-based Message Authentication, Reporting, and Conformance (DMARC) | 2013 | 3.0.8 |
| rfc7505 | A "Null MX" No Service Resource Record for Domains That Accept No Mail | 2018 | 4.5 | |
| rfc7672 | DANE | SMTP Security via Opportunistic DNS-Based Authentication of Named Entities (DANE) Transport Layer Security (TLS) | 2015 | 3.4.2 |
| rfc8301 | DKIM | Cryptographic Algorithm and Key Usage Update to DomainKeys Identified Mail (DKIM) | 2008 | 2.0 |
| rfc8314 | Implicit TLS | Cleartext Considered Obsolete: Use of Transport Layer Security (TLS) for Email Submission and Access | 2008 | 2.0 |
| rfc8446 | TLS 1.3 | The Transport Layer Security (TLS) Protocol Version 1.3 | 2019 | 5.0 |
| rfc8460 | TLS-RPT | SMTP TLS Reporting | 2018 | 4.8 |
| rfc8461 | MTA-STS | SMTP MTA Strict Transport Security (MTA-STS) | 2018 | n/a |
| rfc8463 | Ed25519 | A New Cryptographic Signature Method for DomainKeys Identified Mail (DKIM) | 2018 | 4.7 |
| rfc8601 | Authentication-Results | Message Header Field for Indicating Message Authentication Status | 2021 | n/a |
| rfc8616 | DKIM | Email Authentication for Internationalized Mail | 2024 | 6.2 |
| rfc8617 | ARC | The Authenticated Received Chain (ARC) Protocol | 2018 | 4.7 |
| BIMI | BIMI | Brand Indicators for Message Identification (BIMI) | 2021 | n/a |
| XCLIENT | XCLIENT | XCLIENT extension | 2015 | 3.3 |
| PROXY protocol | PROXY | The PROXY protocol (1 & 2) | 2016 | 3.5 |