shao.dut

$subject = "=?UTF-8?B?".base64_encode($subject)."?=";
$headers = 'MIME-Version: 1.0' . "\n";
$headers .= 'Content-type: text/html; charset=utf8' . "\r\n";
$headers .= "Content-Transfer-Encoding: base64";
$mailtext = base64_encode($mailtext);

Hi Mike. I added these code in email-users.php line 1466. It works fine.

May be you can add a function to let users choose transfer encoding in future versions, put raw html into email body can bring lots of problems.