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

[Ned Freed <[e-mail]>]

> On 16/01/2019 18.17, Ned Freed wrote:

> > As for BINARYMIME, we implemented that for SUBMIT in 2012 due to a
> > couple of customer requests.

> Microsoft, for their hotmail.com service anyway, does support
> BINARYMIME for received mail.  And, as far as I can tell, it works.

> I send a photo with "Content-Type: image/png; charset=binary" and view
> it using their web interface and I see my photo.  Sent it all one big
> fat BDAT.

> Strangely, when Microsoft sends mail they don't seem to use BINARYMIME
> even though I offer the extension.

Likely because they transcoded it to 8bit almost immediately. That's what we
do. There's really no choice because pretty much everyone attaches signatures
these days - specifically DKIM - and once you do that transcoding is no longer
an option. 

Delaying signing or resigning in the event your initial choice to transcode
turns out to be incorrect is pretty unappealing implementation-wise. And even
if we tried to accomodate the minescule number of SMTP BINARYMIME servers out
there, this would result in an increase in delivery failures (for those that
don't/can't transcode), message content (DSN delivery failures when the DSN is
also binary), and DKIM signature breakage.

This is not a difficult call to make.

> Microsoft, so it seems, have overcome the problems that seem to plague
> other email software and service providers with regard to BINARYMIME.

Clearly not, as you yourself have noted.

					Ned