So not only is the final delvery agent incapable of knowing the
client's capabilities, it wouldn't help if it knew at the time of
delivery, because the capabilities might change at any time. And
messages in mailstores last for years, unline messages in transit,
which generally expire after days at most, so it is very possible that
a client's capabilities will change over the lifetime of the message
in the mailstore.
Exactly. That is why it is important that we do not downgrade mail
permanently
if we can avoid it. I reacted to the text because it seemed to be saying
that. Specifically, it says the storage agent may downgrade i18n e-mail.
Does that mean that it would actually downgrade it in the storage,
or just for the purpose of serving it to this particular client at this
one time?
What is knowable is whether or not the *mailbox server* is capable of
supporting UTF8SMTP; in the case of delivery via SMTP or LMTP, the
"UTF8SMTP" extension is a good way of signalling such support.
The issues in the specific context of IMAP and POP, including
identification mechanisms, are addressed in the drafts specific to
these protocols; however, I think it would not be appropriate to go
into details on those protocols in an overview document - also because
those proposals are still under discussion by the WG, and might change
considerably before they are finished.
Fair enough.
I don't know if this is enough clarification of why the text is the
way it is - do you need more information to clear your DISCUSS?
Let me suggest a small reformulation:
Since the final delivery SMTP server (or, to be more specific, its
corresponding mail storage agent) cannot safely assume that agents
accessing email storage will always be capable of handling the
extensions proposed here, it MAY either provide a downgraded
version of the internationalized email to these agents, or
specially identify messages that utilize these extensions,
or both. In any case, the final delivery SMTP server SHOULD allow
the original internationalized forms to be accessed by UTF8SMTP-aware
agents without information loss, even if they are also accessed
in downgraded form by other agents.
