Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 4.0 Message Specification

This specification has been revised 3 times since RFC 2633 (1999). Each document below formally obsoleted the one before it; the versions still in force are listed first.

This lineage is derived automatically from the “obsoletes” relationships recorded in the public RFC Editor index — no editorial judgement is applied to the ordering. The most recent document in the chain is RFC 8551 (April 2019).