Hello Nathaniel --- I can sympathize with where you are coming from,
but I must object to your idea that it is really OK for us to
seriously consider MTA mucking with End-To-End Protocol Data Units
"when it seems like the right thing to do".
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user-oriented concerns
If an MTA is going to perform major transformations on a mail message,
such as translating image formats or mapping between included data and
external-reference data, it seems inevitable that there will be
situations in which users will object to these transformations. This
is, in large part, an implementation issue, but it seems advisable,
wherever possible, to provide a mechanism whereby users can specify, to
their MTA software, whether or not they want such services performed
automatically on their behalf. The use of the "Content-Conversion"
header field, as mentioned above, is suggested for this purpose.
Some have expressed the opinion that format transformations should NEVER
be performed by an MTA. Obviously this is controversial. Certainly, at
a minimum, MTA implementors should consider carefully the needs and
desires of their user community before implementing such a facility.
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What I seriously fear is that if this is published in any RFC, even if
BOLDLY LABELED "INFORMATIONAL -- NOT ANY KIND OF A STANDARD"
we will find sendmail oriented folk out there doing their own thing,
"Because Nathaniel Said We Could!"
Or "Because an RFC Said we could!"
Let me put it into a more confining context:
We are talking about "Major Quality of Service (QOS)a Issues" here!
If we have random sendmail style hackers out there doing their own
thing, we will surely lose our ability to trust our beloved mail
system to deliver with regularity. We cannot allow MTA operators to
unilaterally decide what is right or wrong about messing with
End-To--End Protocol-Data-Units in the Transport Service.
This is like saying that it is OK for IP to mess with the data in its
packets. It is like saying that airline baggage handlers can repack
our suitcases if they think they have a better idea of how it should
be done. The possibilities are endless, and endlessly frightening.
Now, if you want to back up and define these mutant transformer things
as gateways, and write gateway standards, I will go along with the
effort to develop the gateway standards.
What I cannot abide is this idea of libertarian MTA operations.
Cheers...\Stef