User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.5) Gecko/20041217 Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.5) Gecko/20041217 I receive a mail message with the following characteristics: Content-type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable and the mail messages also contains at least one of the following special characters: right single quote character (encoded as ’ ) left double quote character (encoded as #8220; ) right double quote character (encoded as ” ) If I forward this message inline (not as an attachment), Mozilla Mail will send the mail message with the following characteristics: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable I am warned that UTF-8 will be used and my choice is to send the mail or go back to the mail composer. There should be no need to send this mail encoded as UTF-8. These few special characters should be recognized and encoded as text/html, charset=iso-8859-1, quoted printable. Character entity references in the HTML standard are available for these and other common special characters missing from iso-8859-1 as follows: ‘ left single quote ’ right single quote “ left double quote ” right double quote Mozilla Mail recognizes these character entity values in incoming text/html mail messages. Mozilla Mail should use these character entity values or the equivalent numerical values that were in the original message when forwarding mail containing these characters. This should be no need to encode forwarded mail as utf-8. My mail preferences in Edit->Preferences->Mail & Newsgroups->Composition has the box checked to send messages with 8-bit characters as "quoted printable" mime encoding. There is no workaround for this bug. The only way to find these special characters is to meticulously search for them in the message or use a another time-consuming procedure. For example, copy the file as text to an editor (Notepad on Windows, for example) and save the text as ANSI, then strip the file removing all of the high bits from the 8-bit characters. Compare the stripped file to the original to determine which characters are causing Mozilla Mail to use utf-8. Reproducible: Always Steps to Reproduce: 1. create a text message with message a few of these special characters encoded as numeric character entities (right single quote character encoded as ’ ,left double quote character encoded as #8220; , right double quote character encoded as ” 2. send it as text/html to yourself 3. try to forward this mail inline as text/html quoted printable Actual Results: Message can only be sent as utf-8 encoding Expected Results: Send the message as text/html quoted printable

Reproduced with TB 1.0+0320, Win2K. Moving to Core. My test message contained the "‘" and "’" entities. If the test message is not quoted-printable, the entities are included in the forwarded message, but converted to "‘" and "’", and forwarded message is still ISO-8859-1. If the test message is quoted-printable, the charset is indeed switched over to UTF-8, and the characters encoded as "=E2=80=98" and "=E2=80=99".

xref bug 307023

sorry for the spam. making bugzilla reflect reality as I'm not working on these bugs. filter on FOOBARCHEESE to remove these in bulk.

Enable "quoted printable": Open config editor (preferences, advanced, general, config editor button) search for mail.strictly_mime then make it true Change the encoding of outgoing mail to iso-8859-1: Tools → Options → Display → Formatting → Fonts → Advanced... → Character Encodings → Outgoing Mail I could not reproduce it. Thunderbird 52.1.0 (32-bit) Windows 7 64-bit