RFC Errata
RFC 5321, "Simple Mail Transfer Protocol", October 2008
Note: This RFC has been updated by RFC 7504
Source of RFC: IETF - NON WORKING GROUPArea Assignment: art
Errata ID: 6561
Status: Rejected
Type: Technical
Publication Format(s) : TEXT
Reported By: Seiichi Hamada
Date Reported: 2021-04-27
Rejected by: Francesca Palombini
Date Rejected: 2022-03-25
Section 4.1.2. says:
Domain = sub-domain *("." sub-domain)
It should say:
Domain = sub-domain *("." sub-domain)[.]
Notes:
RFC-1034 section 3.1 say " Since a complete domain name ends with the root label, this leads to a printed form which ends in a dot." and also say 'a character string which represents a complete domain name (often called "absolute"). For example, "poneria.ISI.EDU." '.
It is necessary to allow a dot at the end of the domain name.
--VERIFIER NOTES--
As reported by John C Klensin in https://mailarchive.ietf.org/arch/msg/iesg/sAzZQpgOkD75eKQiS-RlWrmPhDk/ : The syntax used in SMTP predates RFC 1034. This possible change was discussed in the DRUMS WG when RFC 2821 was being assembled and rejected as likely to cause harm with existing implementations. If he recalls, that topic was revisited in the YAM WG that developed RFC 5321 with the conclusion to not reopen it.
So it is a substantive matter and not an editorial change and hence, as an erratum, it is rejected.