According to RFC 2231 the filename of e-mail attachments can be encoded,
e.g. with base64 (for example, the Brother ADS2800W Scanner does this).
Here an example how it looks like:
Content-Disposition: attachment; filename="=?UTF-8?B?QlJXMjg1NjVBOEI5RkQyXzIwMTcwNTIzXzIzMDMzN18wMDAzMDMucGRm?="
Signed-off-by: Cornelius Ludmann <dev@cornelius-ludmann.de>