用gmail的web收邮件，正文正常标题会乱码，各位帮帮忙，谢谢

[php]
$to_address = "henryluo@gmail.com";
$from_address = "henryluo@gmail.com";
$subject ='[Blog]'.$post_title;
$message =$content ;
$headers = "From: Henryluo's blog \r\n".
"Reply-To: henryluo@gmail.com \r\n".
'Content-Type: text/plain; charset="utf-8" \r\n'.
"X-Mailer: PHP";
mail($to_address, $subject, $message, $headers);
[/php]