Secure/Multipurpose Internet Mail Extensions Version 4.0 Message Specification
RFC 8551, “Secure/Multipurpose Internet Mail Extensions Version 4.0 Message Specification”, is a Proposed Standard document published in April 2019 by J. Schaad, B. Ramsdell, S. Turner. It obsoletes RFC 5751. It has since been updated by RFC 9788. The canonical text is published by the RFC Editor.
Abstract
This document defines Secure/Multipurpose Internet Mail Extensions (S/MIME) version 4.0. S/MIME provides a consistent way to send and receive secure MIME data. Digital signatures provide authentication, message integrity, and non-repudiation with proof of origin. Encryption provides data confidentiality. Compression can be used to reduce data size. This document obsoletes RFC 5751.
What “Proposed Standard” means
An entry-level standards-track specification: stable, peer-reviewed and a solid basis for implementation, though it may still evolve before becoming an Internet Standard.
The canonical text of RFC 8551 is hosted at rfc-editor.org. Available in TXT,HTML.
- RFC 8550 Secure/Multipurpose Internet Mail Extensions Version 4.0 Certificate Handling
- RFC 8552 Scoped Interpretation of DNS Resource Records through "Underscored" Naming of Attribute Leaves
- RFC 8549 Export of BGP Community Information in IP Flow Information Export
- RFC 8553 DNS Attrleaf Changes: Fixing Specifications That Use Underscored Node Names
- RFC 8548 Cryptographic Protection of TCP Streams
- RFC 8554 Leighton-Micali Hash-Based Signatures
- RFC 8547 TCP-ENO: Encryption Negotiation Option
- RFC 8555 Automatic Certificate Management Environment