MBOX-Line: From tss at iki.fi  Fri Jul  9 20:15:43 2010
To: imap-protocol@u.washington.edu
From: Timo Sirainen <tss@iki.fi>
Date: Fri Jun  8 12:34:45 2018
Subject: [Imap-protocol] folding/encoding of subject in ENVELOPE
In-Reply-To: <alpine.WNT.2.00.1007091852190.2580@Shimo-Tomobiki.Panda.COM>
References: <4C37C781.5060700@sun.com>
	<FCB729DF-4574-4EA5-BA6C-B21F5B67B9D1@iki.fi>
	<alpine.BSF.2.00.1007091831130.49338@legolas.orthanc.ca>
	<alpine.WNT.2.00.1007091852190.2580@Shimo-Tomobiki.Panda.COM>
Message-ID: <0D64214F-14CE-43EB-AFC8-9E00DE63EC7F@iki.fi>

On 10.7.2010, at 4.00, Mark Crispin wrote:

> On Fri, 9 Jul 2010, Lyndon Nerenberg wrote:
>>> Yes, but my server (and many others) are converting all whitespace to a
>>> single space (tabs, folds, multiple spaces, etc). I can't exactly
>>> remember why, though. Maybe I implemented it only because others did
>>> that too..
>> The '822 <FWS> grammar production.
> 
> Correct.  You interpret the fields as per RFC 822 (etc.).
> 
> Line folding is an RFC 822 (etc.) concept and is not part of the field
> data (e.g., Subject).  Header fields are logically a single line, even if
> they are multiple lines in the header.

But it's not just the line folding. All LWSP containing tabs, spaces and CRLFs are converted into a single space by many servers (IIRC also UW-IMAP). RFC 822 says that all LWSP is equivalent to a single space in structured fields, but subject is unstructured field.

> Arguably, a future version of IMAP should decode MIME encoded-words into
> UTF-8.

I'm looking forward to RFC 5738bis.


