At 02:54 PM 3/5/2005 +0000, you wrote:
I like the concept of MDA and want to distinguish it more clearly from the
MTA.
I would suggest the MTA only works with domain part of the message, the
MDA with domain parts and local parts.
So the MTA does the transfering, the MDA does all the rest.
If an operation needs the localpart of the address it is a MDA function.
(auto responders, mailinglist actions, the SMTP VRFY, EXPN, ETRN commands
ect.)
I agree, and I think a clear distinction between MTA and MDA is also useful
in discussions of spam. Filtering, flagging, and blocking should be done
by the MDA, which is aware of all its recipients and their
preferences. Domain authentication should done by the incoming MTA, which
can enforce a site-wide policy such as "any sender that doesn't
authenticate, abort the session, don't download anything". Its a clean
interface, with the possible exception that some recipients might want an
individual policy, like "send me everything, even if it doesn't authenticate".
The concept of administrative domains is also useful in discussing when
authentication should occur (at the incoming MTA for each domain). A clear
standard here will allow a recipient to quickly sort through piles of
headers, skipping past multiple Received lines from within his own domain
and any domains of trusted forwarders, and getting straight to the domain
that needs to be blocked or filtered.
-- Dave
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* David MacQuigg, PhD * email: dmq'at'gci-net.com * *
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