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CurrentPROPOSED STANDARDIETF stream

RFC 9788: Header Protection for Cryptographically Protected Email

In plain English — editorial summary, not part of the RFC

S/MIME version 3.1 introduced a mechanism to provide end-to-end cryptographic protection of email message headers. However, few implementations generate messages using this mechanism, and several legacy implementations have revealed rendering or security issues when handling such a message. This document updates the S/MIME specification (RFC 8551) to offer a different mechanism that provides the same cryptographic protections but with fewer downsides when handled by legacy clients. Furthermore, it offers more explicit usability, privacy, and security guidance for clients when generating or handling email messages with cryptographic protection of message headers. The Header Protection scheme defined here is also applicable to messages with PGP/MIME (Pretty Good Privacy with MIME) cryptographic protections.

Document record

Document ID
RFC9788
Published
August 2025
Authors
D. K. Gillmor; B. Hoeneisen; A. Melnikov
Status
PROPOSED STANDARD
Stream
IETF
Area
sec
Pages
218
Also known as
—
Updates:
RFC 8551

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The document record above — title, authors, date, status, stream, area, relationships, DOI and errata — is imported verbatim from the public RFC Editor index. The “in plain English” section is editorial: written by The metasystema editorial team, not part of the RFC. Where the two differ, the RFC text governs.

Last checked against the RFC Editor index on . RFCs are never revised after publication; changes are issued as new documents.

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