este es el codigo que uso:
Código PHP:
headers = "MIME-Version: 1.0\r\n";
$headers .= "From: Foo \r\n";
$headers .= "Subject: Test mail\r\n";
$headers .= "Content-Type: multipart/alternative;boundary=" . $uniqueid. "\r\n";
$message .= "\r\n\r\n--" . $uniqueid. "\r\n";
$message .= "Content-type: text/html;charset=utf-8\r\n\r\n";
$message .= 'hola';
mail('[email protected]', 'titulo', $message, $headers);