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Status:

PROPOSED STANDARD

Author:

J. Fenton

Stream:

IETF

Source:

uta (sec)

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DOI:  https://doi.org/10.17487/RFC8689

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Abstract

The SMTP STARTTLS option, used in negotiating transport-levelencryption of SMTP connections, is not as useful from a securitystandpoint as it might be because of its opportunistic nature;message delivery is, by default, prioritized over security. Thisdocument describes an SMTP service extension, REQUIRETLS, and amessage header field, TLS-Required. If the REQUIRETLS option orTLS-Required message header field is used when sending a message, itasserts a request on the part of the message sender to override thedefault negotiation of TLS, either by requiring that TLS benegotiated when the message is relayed or by requesting thatrecipient-side policy mechanisms such as MTA-STS and DNS-BasedAuthentication of Named Entities (DANE) be ignored when relaying amessage for which security is unimportant.

For the definition ofStatus,seeRFC 2026.

For the definition ofStream, seeRFC 8729.