draft-hall-inline-dsn-01 (was: [Asrg] Re: bounces, and anit-spam princip

On 2007-01-23 16:27:12 -0500, Eric A. Hall wrote:
> On 1/23/2007 4:00 PM, Peter J. Holzer wrote:
> > > MTA-resident complex content filtering with different per-recipient
> > > outcomes is not compatible with recipient enumeration preceding the
> > > data block;
> > It can still be done. It just needs a bit of trickery with 4xx replies.
> > It's ugly as hell, and it increases mail traffic (and CPU usage for
> > filtering), but it works.
> see http://www.ehsco.com/misc/I-Ds/draft-hall-inline-dsn-01.txt which uses
> per-recipient codes after the data block (the LMTP model)
I meant "it can be done without extensions to SMTP". With extensions it
can be done in a much cleaner way, of course; but that needs support in
both the client and the server.

A few quibbles about your draft (which I'm tempted to implement in
qpsmtpd if someone implements the client side):

The name INLINE-DSN doesn't describe well what it does. To me, a DSN
is more than an SMTP reply, it's an entire message explaining what
happened to the mail, and your extension doesn't send that.
Something like DATA-RCPT-RESULT would be more descriptive (not that an
SMTP client will care much about the meaning of the bytes it sends).

I'm a bit dubious about the use of 3xx status codes. In the other cases
where they are used (DATA, SMTP AUTH, ...) they are used to indicate to
the client that it should send more data to complete the current
command, not that it should send another command. It's a clever way to
defer only some recipients until after data, though.

Finally a question: How is it determines which of the response codes
after DATA corresponds to which recipient? Do they have to be in the
same order or do they have to include the recipient address? Your
examples show both, but the text isn't clear.

        hp


-- 
   _  | Peter J. Holzer    | I know I'd be respectful of a pirate 
|_|_) | Sysadmin WSR       | with an emu on his shoulder.
| |   | hjp(_at_)hjp(_dot_)at         |
__/   | http://www.hjp.at/ |    -- Sam in "Freefall"

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