At 2:12 PM -0500 2003/10/02, Bill Weinman wrote:
My research suggests that a significant number of corporate and community
(co-ops, municipalities, user groups, etc.) admins want server-wide
policies.
Agreed.
ISPs have more complex needs and will use per-recipient
settings, and even some per-sender settings. (Note that per-sender
settings *can* be advertised in the EHLO reply.)
Also true. The issue is that the protocol must be designed so as
to handle the more complex case, while the simpler case falls out
naturally.
And you do have to keep in mind how to handle situations where
the backup MXes do not have the same policies as the primaries, or
where they may not be MCP-enabled at all.
That's done in the RCPT response. You seem to be suggesting a
per-recipient advertisement of MPC values. I decided against that to
keep down the number of round-trips. As the spec currently stands, a
client doesn't get per-user MPC values, it just gets 250 or 550 (or
occasionally 451) reply codes for each RCPT.
You could advertise site-wide policies in the EHLO greeting, but
otherwise you could only advertise that your server is MCP-enabled,
which may have some impact in the interpretation of SMTP reply codes
or extended response codes.
Do you mean "senders that ignore the MPC values in the EHLO response"?
They will get a 550 later in the conversation. And they risk getting
added to a CRL.
If the sender is not MPC-enabled, you might end up blacklisting
your backup MX. If you ensure that doesn't happen, what you
guarantee is that people can by-pass your MPC settings by going
through the backup MX instead.
Putting us right back to where we are today.
Backup AMTP servers may well need some extra logic. I will give that
some more thought and see if I can find something that needs to be
addressed in the spec.
Even if you can't solve the problem, you need to be explicit in
the acknowledgement of the issue and point out what the
administrators will need to do.
--
Brad Knowles, <brad(_dot_)knowles(_at_)skynet(_dot_)be>
"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety."
-Benjamin Franklin, Historical Review of Pennsylvania.
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