Ist der Email-Server bei Hotmail geblockt?

Ich bekam bei einer Mail an ....@hotmail.com folgende Meldung:

This is the mail system at host mailout08.t-online.de.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                   The mail system

<..............@hotmail.com>: host
    hotmail-com.olc.protection.outlook.com[104.47.10.33] said: 550 5.7.1
    Unfortunately, messages from [194.25.134.20] weren't sent. Please contact
    your Internet service provider since part of their network is on our block
    list (S3150). You can also refer your provider to
    http://mail.live.com/mail/troubleshooting.aspx#errors.
    [DB5EUR03FT034.eop-EUR03.prod.protection.outlook.com] (in reply to MAIL
    FROM command)