Quick initial thoughts on first reading of submitter-00
Section 4.
Typo: xtest should be xtext.
Section 4.1. Para (c) right at the end.
For consistency with the requirements ealier, the SUBMITTER
parameter is only mandatory if it differs from the MAIL FROM. If
a mailing list sets the MAIL FROM and Sender to the same value,
then it seems that it doesn't need to add a SUBMITTER as well.
Section 4.2. When, at some future time, use of the SUBMITTER
parameter becomes MANDATORY, SMTP servers MAY use the MAIL FROM
address as the purported responsible domain in the absence of the
SUBMITTER parameter.
Presumably they may also continue to use the purported responsible
address from the headers if they prefer? Or even use both?
Section 4.3.
I think the SHOULD ought to be a MUST, in order to ensure
interoperability between MTAs that support the extension and MTAs that
don't.
As specified, a SUBMIT-aware MTA is permitted to refuse to forward
mail on to an MTA that is not SUBMIT-aware. I can't see what that
gains, other than a strong disincentive against using the SUBMITTER
parameter.
-roy