I'm generating a MIME message with an attachment whose
filename includes non-ASCII characters.  I create the
MIME header as follows:

msg.add_header('Content-Disposition', 'attachment',
filename=u'Fu\xdfballer_sind_klug.ppt')

The Python-generated header looks like this:

Content-disposition:
=?utf-8?b?YXR0YWNobWVudDsgZmlsZW5hbWU9IkZ1w59iYWxsZXJf?=
        =?utf-8?q?sind=5Fklug=2Eppt=22?=

I sent messages with this header to Gmail, evolution,
and thunderbird, and none of them correctly decode that
header to suggest the correct default filename. 
However, I've found that those three mailers do behave
correctly when the header looks like this instead:

Content-disposition: attachment;
filename="=?iso-8859-1?q?Fu=DFballer=5Fsind=5Fklug=2Eppt?="

Is there a way to make Python's email module generate a
Content-disposition header that works with common MUAs?
 I know I can manually encode the filename before
passing it to add_header(), but it seems that Python
should be doing this for me.