Comment 44 for bug 233990

Created an attachment (id=417890)
mail folder file

Attached mail folder file:
  mail-1 : Sent mail.
           Generated by Sm2 and Subject: is manually crafted.
           - Sm2 puts each rfc2047 encoded word in single header line.
           - Two header lines are merged into single herader line manually.
  mail-2 : Return receipt by Tb 3 on MS Win.

(In reply to comment #4)
> I'm not sure what you're showing us (a From: and a To:).
> Sending? Received? Return Receipt? Normal Mail?
> Please provide full files showing everything you did, like mine do.

You can't understand next?
> Original From: in mail with MDN=on. ({CRLF}==0x0D0A)
> (a) > From: =?ISO-2022-JP?B?GyRCT0JFRDh3OTAbKEI=?= <email address hidden>{CRLF}
> Tb3 generated following To: in return receipt.
> (b) > To: =?ISO-2022-JP?B?GyRCT0JFRDh3OTAbKEI=?={CRLF}
> > <email address hidden>{CRLF}

1. Some one(Tb, Seamonkey) sends a mail with From: of (a),
   with requesting return receipt.
2. Tb 3 receives the mail, and sent return receipt according to MDN request.
3. To: in the "return receipt sent by Tb3" was (b).
   {CRLF} was inserted at same position as {LF} in comment #0.

> It wouldn't be surprising that the problem did not exist on Windows, because
> EOL is CRLF on Windows and LF on Linux. This is a Linux Thunderbird bug.

Problem does exist in Tb 3 on MS Win too. {CRLF} was surely inserted by Tb 3.
On MS Win, inserted bytes was {CRLF}. So RFC2822 violation won't occur fortunately.
"unneeded folding of To:" was observed on MS Win too.
As From: (by Tb, Seamonly) is following,
> From: =?ISO-2022-JP?B?GyRCT0JFRDh3OTAbKEI=?= <email address hidden>
next is sufficient for To: of "return receipt"(shorter than the From:).
> To: =?ISO-2022-JP?B?GyRCT0JFRDh3OTAbKEI=?= <email address hidden>
Similar "folding after each RFC2047 encoded word" is also observed for Subject: header.
See attached mail folder data.

I guess that problem is "new line of OS is inserted upon header folding by Tb on any OS" instead of "Tb on Linux only inserts bare LF wrongly".
And, I guess the header folding is for avoiding RFC violation(e.g. too long header generated by original mail sender).
I think attached mail data indicates;
  Tb folds mail header after each rfc2047 encoded word.