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Re: Re: draft-crocker-email-arch-03 Users, MDA and administrative domains

2005-03-05 12:38:40

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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