Looks like Xepher.net has been added to a block list on hotmail.com and live.com.
Quotehost
hotmail-com.olc.protection.outlook.com[104.47.70.33] said: 550 5.7.1
Unfortunately, messages from [198.74.48.54] weren't sent. Please contact
your Internet service provider since part of their network is on our block
list (S3140). You can also refer your provider to
http://mail.live.com/mail/troubleshooting.aspx#errors.
[BN7NAM10FT044.eop-nam10.prod.protection.outlook.com] (in reply to MAIL
FROM command)