From draft-gellens-format-01.txt
[Quoted-Printable] encoding SHOULD NOT be used with Format=Flowed
unless absolutely necessary (for example, non-US-ASCII 8-bit
characters over a strictly 7-bit transport such as unextended SMTP).
If Quoted-Printable is used, it SHOULD NOT be used to protect the
trailing space.
.
.
the safer course is to not protect the trailing spaces unless the
body part is cryptographically signed.
This overrides RFC2045 (where trailing spaces MUST be protected or
deleted when generating qp, and must be deleted when removing qp).
This means that an MUA wishing to support format=flowed would have to
consider the media type before removing the transfer-encoding. It would
also have to consider the context of the text part - whether or not it
has been digitally signed.
It is surely a serious and unacceptable layer-violation to make an MUA
consider how a MIME part is going to be dealt with before it can decide
how to remove a transfer-encoding.
The intent of Format=Flowed is to allow user agents to generate
flowed text which is non-obnoxious when viewed as pure Text/Plain;
use of Quoted-Printable hinders this and may cause Format=Flowed to
be rejected by end users.
QP does not hinder the stated intent when sent to MIME-capable MUAs, it
is only when QP is sent to non-MIME recipients that problems arise.
Perhaps the wording should be aimed at dissuading MUAs from using qp
when the recipients' MUAs are not known to support MIME. This would be a
good thing in itself, but almost certainly a lost cause :-(
--
Ian Bell T U R N P I K E Ltd