Chris Newman just pointed out that there is a conflict between an
Enhanced Status Code defined in RFC 4468 and draft-siemborski-rfc2554bis.
RFC 4468 defines:
X.7.8 Trust relationship required
The submission server requires a configured trust relationship
with a third-party server in order to access the message content.
535 5.7.8 Authentication credentials invalid
This response to the AUTH command indicates that the authentication
failed due to invalid or insufficient authentication credentials.
In this case, the client SHOULD ask the user to supply new
credentials (such as by presenting a password dialog box).
Use of 5.7.8 in draft-siemborski-rfc2554bis-08.txt is a new feature
since RFC 2554. However, draft-siemborski-rfc2554bis was around for long
time and there might be more implementations of its 5.7.8 than that from
the RFC 4468. There are certainly fewer RFC 4468 implementations
deployed at the moment.
So, in order to decide whether draft-siemborski-rfc2554bis needs to be
changed or whether rfc4468bis needs to be published, I would like to
solicit comments from implementors of both extensions.