I'm using KMail. When I send a mail from Hotmail's web interface it is sent without any problem. However when I use KMail and hotsmtpd, _every_ mail I sent is returned with a Delivery Failure Notification.
All of my sends fail if they have WMV attachments. My other emails, both HTML and text, go out fine.
Because there is no longer any current online documentation, I have not yet figured out where the problem is. The answer may possibly lie in a very old FAQ that has been archived, but I have just discovered it and so have not yet searched for it. The link is here: http://web.archive.org/web/20040915080542/hotwayd.sourceforge.net/faq/