From: Keld J|rn Simonsen <keld(_at_)dkuug(_dot_)dk>
qouted-printable/quoted-readable is used for transferring "plain text".
It should not be used with anything else but "plain text".
And the objective of it is to be read by humans.
I think there is no real concern about trailing blanks here.
People do not care if there are trailing blanks at the end of the
line when they read their mail. At least I do not notice.
I'm not sure it is safe to assume that quoted-printable is specifically for the
purpose of transferring "plain text". For instance, if I want to send document
via email that must be preserved bit-for-bit to be used by the recipient, but
still is "mostly printable ASCII", then I would argue that quoted-printable is
a good encoding for the job.
I think the quoted-printable encoding is a good way to transmit, for instance,
UNIX Makefiles, sendmail configs, and other ASCII files that have embedded HT
(horizontal tab) charcters; documents for word processors that use some kind of
extended ASCII; and ASCII files with lines longer than seventy-eight
characters. Of course, in order to be transmitted intact across the various
mail "enclaves", the encoded form of such documents would still have to be
represented in a subset of the characters that can be expressed in all of the
character encodings we use. (It might be useful to publish a suggested set of
characters to use when sending binary files via quoted-printable encoding, to
minimize the liklihood that they will be munged in transit by non-ASCII mail
systems.)
Now, in a sense, this leaves us with two kinds of quoted-printable encoding:
one to be used to transmit "plain text" files, and another to be used to
transmit "binary" files. This doesn't bother me, since the same decoder will
work with either, and implementation of quoted-printable-encoding-for-binary
files in the sender's UA would be entirely optional. (As long as we aren't
insisting that a particular content-encoding always be used with a particular
content-type).
I therefore think it's worthwhile to "tighten-up" the definition of
quoted-printable so that it can be used to transmit mostly-printable-ASCII
binary files intact from end to end, and still keep them readable for those
without fancy decoders.
Keith