RFC6331: Moving DIGEST-MD5 to Historic

Dear @ruby team,

In first, I wish you a Happy New Year!

20 November 2008: CRAM-MD5 to Historic:

• https://tools.ietf.org/html/draft-ietf-sasl-crammd5-to-historic-00

29 June 2017: CRAM-MD5 to Historic:

• https://tools.ietf.org/html/draft-zeilenga-luis140219-crammd5-to-historic-00

July 2011: RFC6331: Moving DIGEST-MD5 to Historic:

• https://tools.ietf.org/html/rfc6331

August 2021: RFC9051: Internet Message Access Protocol (IMAP) - Version 4rev2:
"Replaced DIGEST-MD5 SASL mechanism with SCRAM-SHA-256. DIGEST-MD5 was deprecated."

• https://tools.ietf.org/html/rfc9051

I add same about SCRAM-MD5.

There are now:

• July 2010: RFC5802: Salted Challenge Response Authentication Mechanism (SCRAM): SASL and GSS-API Mechanisms: https://tools.ietf.org/html/rfc5802 (SCRAM-SHA-1 and SCRAM-SHA-1-PLUS)
• July 2010: RFC5803: Lightweight Directory Access Protocol (LDAP) Schema for Storing Salted: Challenge Response Authentication Mechanism (SCRAM) Secrets: https://tools.ietf.org/html/rfc5803
• November 2015: RFC7677: SCRAM-SHA-256 and SCRAM-SHA-256-PLUS: Simple Authentication and Security Layer (SASL) Mechanisms: https://tools.ietf.org/html/rfc7677

Soon:

• SCRAM-SHA-512(-PLUS): https://tools.ietf.org/html/draft-melnikov-scram-sha-512
• SCRAM-SHA3-512(-PLUS): https://tools.ietf.org/html/draft-melnikov-scram-sha3-512

No implementation file or test is named. Start by reviewing net-smtp's current authentication mechanisms alongside RFC6331, RFC9051, and the SCRAM references in the issue. Done requires a maintainer decision on the intended treatment of DIGEST-MD5 and SCRAM-MD5 and a concrete implementation scope.