On Sat 26 Nov 2022, at 16:01, David Wright <deb...@lionunicorn.co.uk> wrote:
> On Sat 19 Nov 2022 at 20:38:46 (+0000), Gareth Evans wrote:
>> On Sat 19 Nov 2022, at 20:15, Gareth Evans <donots...@fastmail.fm> wrote:
>> [...]
>> > I'm not sure this is a Tb bug, just perhaps a "purist" way of doing 
>> > things ...
>> 
>> I had assumed no blank line preceding a boundary was required as Tb still 
>> processes the boundary without one, but
>> 

>> https://www.rfc-editor.org/rfc/rfc2049.html#page-15
>> 
>> suggests this is in fact a requirement.  So perhaps a bug.

> I don't see where the RFC talks about blank lines.

Hi David,

It doesn't, save for one mention in the appendix, and that was sort of my 
point...

> The text part of my emails (where they include an attachment) end
> as usual with the characters "David.<Newline>", and that Newline
> is the last character of mine. It's then followed by another
> Newline which is the start of the Unique Boundary Marker.
>
>   David.<Newline><Newline>BOUNDARY MARKER
>           ↑  ↑    ↑     ↑
>           mine    marker's
>

> That pair of Newlines give the appearance of a blank line, which
> you assume is necessary.

Well... I meant "suggests" literally, because...

At the time of writing the message you refer to above, I had taken the Appendix 
A example in RFC2049 ("[MIME] ... Conformance criteria and examples") to be 
prescriptive by example (a "conformance example"!), given blank line 
requirements are less than definitively spelt out there.

RFC1521, obsoleted by 2049, includes:

"  7.2 ... Each part
   starts with an encapsulation boundary, and then contains a body part
   consisting of header area, *a blank line*, and a body area ... 
   NO header fields are actually required in body parts.  A body part that 
   starts with a blank line, therefore, is allowed ..."

https://www.rfc-editor.org/rfc/rfc1521

but this text does not appear in RFC2049, where the notion is merely implied in 
a bracketed note in an example in an appendix, which also contains the only 
appearance of "blank".

"Appendx A -- A Complex Multipart Example

[...]

 MIME-Version: 1.0
     From: Nathaniel Borenstein <n...@nsb.fv.com>
     To: Ned Freed <n...@innosoft.com>
     Date: Fri, 07 Oct 1994 16:15:05 -0700 (PDT)
     Subject: A multipart example
     Content-Type: multipart/mixed;
                   boundary=unique-boundary-1

     This is the preamble area of a multipart message.
     Mail readers that understand multipart format
     should ignore this preamble.

     If you are reading this text, you might want to
     consider changing to a mail reader that understands
     how to properly display multipart messages.

     --unique-boundary-1

       ... Some text appears here ...

     *[Note that the blank between the boundary and the start
      of the text in this part means no header fields were
      given* [...]

     --unique-boundary-1
     Content-type: text/enriched

     This is <bold><italic>enriched.</italic></bold>
     <smaller>as defined in RFC 1896</smaller>"

https://www.rfc-editor.org/rfc/rfc2049.html#page-15

There are blank lines between part header fields and content - but this 
requirement is implied rather than specified in terms, as it is in 1521.  

There are blank lines between content and following boundaries - this may be 
for readability purposes, but at the time, I thought this suggestive of 
requirement.

I read somewhere else (which I now can't find) that a boundary must be preceded 
by a CRLF, which is considered part of the boundary - but not necessarily a 
blank line.

Best wishes,
Gareth


>
> If there were only one Newline, it would belong to the marker,
> and my text would finish at the Period. You can sometimes
> observe this with non-text parts because, for example, HTML
> parsers don't necessarily care whether </html> is followed
> by Newline.
>
> Cheers,
> David.

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