[Email-SIG] header folding

[Stephen J. Turnbull]

R. David Murray writes:

 > Hmm.  Makes sense to me.  So you'd rather the method were called "fold"
 > and that refold_source remains the name of the policy control.

Yes.

 > What's the word for what is done when a text message is made to have
 > a line length of less than 78 by using quoted printable (or base64)
 > encoding?

RFC 2045 discusses "insertion of soft line breaks"; it doesn't mention
a term like "folding".  "Folding" seems like a good term to me,
though.  Note that the RFC 2045 definition of quoted-printable says
that physical line length MUST be 76 characters or less, including any
terminating = but not the CRLF pair that separates lines.

 > Can anyone see a use case for controlling folding of headers
 > separately from folding of message bodies?  I haven't thought of
 > one, which is why I'm thinking one policy knob controls both.

The RFCs' treatments differ somewhat.  RFC 5322 has both a MUST NOT
and a SHOULD NOT exceed limit on line length (998 and 78 characters,
not including the CRLF, respectively).  RFC 2045 quoted-printable has
only the MUST NOT limit of 76 (but the difference in limits is not a
big deal).

It's not clear to me what exactly the policy knob you're talking about
is for body text.  There is no policy really allowed if quoted-
printable is being used.  So the policy knob is whether to use
quoted-printable to limit physical line length?

The only reason I can think of for having separate controls is that
many MUAs mishandle quoted-printable in the body text.  Patches don't
apply, one-time-key URLs in links get broken and fail to be
recognized.  On the other hand, header-folding rarely has such
consequences in my experience.