RFC 9598 was recently published to resolve an issue in the encoding of the domain-part of internationalized email addresses.
Specifically, the domain-part must always contain LDH labels (IDNA labels must be expressed in their A-label representation and must not use U-labels). This simplifies the previously complex logic specified in RFC 8398 that was difficult to implement and resulted in several CVEs for a very popular library (CVE-2022-3786, CVE-2022-3602, CVE-2022-4203).
SMBR should be amended to reference RFC 9598 so that domain-parts in SmtpUTF8Mailbox align with the new specification.
Side note: This is also very likely the reason why S/MIME certificates with IDNA are (more or less) broken in Thunderbird and Apple Mail. Even if you use the A-label.
RFC 9598 was recently published to resolve an issue in the encoding of the domain-part of internationalized email addresses.
Specifically, the domain-part must always contain LDH labels (IDNA labels must be expressed in their A-label representation and must not use U-labels). This simplifies the previously complex logic specified in RFC 8398 that was difficult to implement and resulted in several CVEs for a very popular library (CVE-2022-3786, CVE-2022-3602, CVE-2022-4203).
SMBR should be amended to reference RFC 9598 so that domain-parts in SmtpUTF8Mailbox align with the new specification.