917720 - Subject: =?ISO-8859-1?Q??= should display empty subject

Status: RESOLVED INVALID

(Thunderbird :: Message Reader UI, defect)

Description

[thomas.hebinck]

Attachment: mail.eml

User Agent: Mozilla/5.0 (Windows NT 5.2; rv:24.0) Gecko/20100101 Firefox/24.0 (Beta/Release)
Build ID: 20130909203154

Steps to reproduce:

I have mails like this:

Date: Wed, 01 Jan 2020 00:00:00 +0100
Subject: =?ISO-8859-1?Q??=
MIME-Version: 1.0
Content-Type: TEXT/plain; CHARSET=iso-8859-1



Actual results:

With TB17, an empty subject was displayed.
After upgrading to TB 24.0, the encoding is shown.


Expected results:

The subject should be empty.

Comment 1

[Masatoshi Kimura [:emk]]

http://www.ietf.org/rfc/rfc2047.txt
>   encoded-word = "=?" charset "?" encoding "?" encoded-text "?="
>   encoded-text = 1*<Any printable ASCII character other than "?"
>                     or SPACE>

"=?ISO-8859-1?Q??=" is invalid as an encoded word because at least one character is needed. Thunderbird 17 incorrectly decoded the "encoded word", then Thunderbird 24 fixed the bug.