Re: [EAI] MTA -> Final delievery MTA -> MDA (Re: MIME questions)

[John C Klensin <klensin at jck.com>]

--On Monday, 26 March, 2007 21:02 +0300 Kari Hurtta
<hurtta+gmane at siilo.fmi.fi> wrote:

> Frank Ellermann <nobody at xyzzy.claranet.de> writes
> on gmane.ietf.ima:
> 
>> Charles Lindsey wrote:
>> 
>> > If the MIME structure of broken, then Garbage-in
>> > Garbage-out. That is already true with out UTF8SMTP.
>> 
>> Kari's proposal would bounce anything misidentified
>> as message/utf-8 at the final delivery MTA, if the
>> LMTP-MDA says "no, thanks, legacy mailbox".  That's
>> not GiGo, it's more like "garbage in, garbage back".
> 
> Lets look one possibility when downgrade fails.
> 
>         C   is SMTP clent
>         F   is is final delivery MTA
>         D   is MDA
> 
> C -> F      is SMTP
> F -> D      is LMTP
> 
>          Lets assume that there is two new SMTP reply codes
> (used              after final dot)
> 
>          ABC             Some recipeints do not support
> UTF8SMTP,                          downgrade failed, retry
> with one RCPT TO                          on transaction
> 
>          XYZ             All recipeints do not support,
> downgrade failed
> 
>          XYZ             LMTP:  This recipeint does not support
>...
>      F -> D        DATA
>      F <- D        354 Start mail input; end with <CRLF>.<CRLF>
>...
>      F -> D        Your case #XCVXBX is closed.
>      F -> D        .                  
>      F <- D        250 Message parsed, UTF8SMTP detected
>      F <- D        250 <client at example.com> sttored
>      F <- D        XYZ <boss at example.com> UTF8SMTP not accepted

Note, fwiw, that the last three lines above violate 2821 (first
two lines must have continuation markers, at least) and that,
unless things have changed recently, many MTAs will assume that
the  return codes on all members of a continuation set will be
the same.

      john


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