Re: [ietf-smtp] [Proposal] confusing parts of the mail system, was 250-MARKDOWN

[Ned Freed <[e-mail]>]

> On 17/01/2019 04.29, Ned Freed wrote:

> > Clearly not, as you yourself have noted.

> Microsoft supports BINARYMIME for received mail on port 25.

> This something that, I hear, is very difficult for others to do.  I'm
> told it's very complicated.  Somehow they have figured out how to make
> this work.

They have not figured out how to make it work, because it's not possible to
make it work in general. Transcoding destroys DKIM signatures, period. So they
either:

(1) Reject messages sent with BINARYMIME and signatures, either in all cases
    or in cases where they know they are going to forward, leading to
    unncessary failures, or,

(2) Accept such messages and trash the signatures, leading to unnecessary
     failures, and,

(3) Deal with dynamic forwarding cases either by not having any or
    falling back to (1) or (2), leading to unnecessary failures.

My guess is that the number of BINARYMIME messages they get via SMTP is
so tiny they haven't had to deal with the problems. And of course since
the people attempting to send them BINARYMIME encounter problems they
probably give up on the extension.

				Ned