PHP邮件损坏附件

Question

I have a form to send form with attachments to email.

It works fine to send files to gmail adresses (on thunderbird client), but to adresses like @company.com on outlook, the attachements came corrupted.

This is what i have in header and body :

    //header
    $headers = "MIME-Version: 1.0
";
    $headers .= "From:".$sender_email."
";
    $headers .= "Reply-To: ".$sender_email."" . "
";
    $headers .= "Content-Type: multipart/mixed; boundary = $boundary

";

    //message text
    $body = "--$boundary
";
    $body .= "Content-Type: text/plain; charset=ISO-8859-1
";
    $body .= "Content-Transfer-Encoding: base64

";
    $body .= chunk_split(base64_encode($message));