如何发送UTF-8编码的电子邮件？

Question

I have inherited a script that sends some content out in three languages (all on same content - repeated) however when recieved the content characters are broken for what i assume is a UTF-8 issue.

Am i right all i need to do is change the charset part to utf-8, or does anything else need to change like the 7bit part ?

you can see where I inserted one UTF-8 reference (not tested yet)

there was something here http://bitprison.net/php_mail_utf-8_subject_and_message which seems to reference base encoding, but I'm not sure if I need that here ?

// Contruct message body.
$body = "";

// Add message for non-mime clients.
$body .= "This is a multi-part message in MIME format.
";

// Add text body.
$body .= "
--$boundary
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit

" . $textContent;

// Add HTML body.
$body .= "
--$boundary
Content-Type: text/html; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit

" . $htmlContent;

mail( $row["email"], "Update Your ArtsDB Listing", $body, $headers );

I looked on another post on here for an a example.

$body .= "
--$boundary
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit

" . $textContent;

// Add HTML body.
$body .= "
--$boundary
Content-Type: text/html; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit

" . $htmlContent;

Answer 1

You are using Content-Type: text/plain; charset=UTF-8 to tell the mail reader that such message part uses UTF-8, which is fine, but... What does the $textContent variable contain? That's the important bit. According to Content-Transfer-Encoding: 7bit, it's a 7 bit encoding so it can't be raw UTF-8. However, you are not using any of the usual 7-bit encodings used for e-mail. Otherwise, there would be a (e.g.) Content-Transfer-Encoding: quoted-printable header.

To sum up, you need to:

1. Have a source string that contains valid UTF-8.
2. Pick a encoding for the transfer, such as quoted_printable_encode().
3. Add a header to tell which transfer encoding you chose.

You could also send the raw UTF-8 as-is and set Content-Transfer-Encoding: 8bit but I would not recommend it. You risk breaking the SMTP standard just by sending very long lines. Also, you have no idea of what kind of legacy programs this will go through.

E-mail is harder than it seems, that's why sooner or later you end up using a third-party library: PHP Mailer, Swift Mailer, PEAR Mail...