[Dovecot] >From escaping

[Mark E. Mallett]

On Tue, Oct 05, 2004 at 05:55:27PM +0300, Timo Sirainen wrote:
> >  (and in fact mutt, up to 1.4.2.1 at
> >least, is broken in the way it recognizes "From " lines if the
> >content-length is missing: specifically, it would recognize "From " 
> >lines
> >even if not preceded by a blank line.. I patched it here.)
> 
> I don't think From-line has to be preceded by empty line? My 
> understanding is that mbox works like:
> 
> From ... LF
> message text
> LF

Depends on your semantics I think :-)  An entire message in an mbox ends
with a blank line, so anything but the first "From " line in a mbox will
be preceded by a blank line.  Thus a naive way to find the start of a new
message is to look for "From " lines following a blank line, and this is
one of the things that ">From "quoting is all about.

At any rate, I ran across cases where there would be:

     some non-blank text in the middle of a message body
     From <valid-looking From line syntax>

and mutt, when there was no Content-length and it was trying to find the
next message boundary, would see this as the start of a new message.
Every other mail program that I tried would get it right; mutt did not.
The unquoted "From " does occur in the wild when not following a blank line;
it's fairly standard *not* to quote a "From " line that does not follow
a blank line.  For example, see:

   http://www.ietf.org/internet-drafts/draft-hall-mime-app-mbox-02.txt

which attempts to summarize or reference some of the accepted variations
on mbox formats.

Also, I think mutt's (and others) use of Content-length is an
optimization that lets it avoid scanning every mbox line to skip from
one message to the next, but doesn't relieve it of the necessity of
"From " line quoting.

mm