mail question

Hello,
Since some time mail from my server is blocked as it looks like SPAM I think. I am not sure though. A customer gets this mails back.
Which makes me think it is something what blocks the mails from my server. I am sure there is no spammer on my server, I know all my customers personally.

Any helpfull thoughts?
Best regards,
Rob

This is the mail system at host myhost.nl.
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
<[email protected]>: host
hotmail-com.olc.protection.outlook.com[some-IP] said: 550 5.7.1
Unfortunately, messages from [myhosts-ip-address] weren't sent. Please contact
your Internet service provider since part of their network is on our block
list (AS3150). You can also refer your provider to
http://mail.live.com/mail/troubleshooting.aspx#errors.
[VE1EUR02FT031.eop-EUR02.prod.protection.outlook.com] (in reply to MAIL
FROM command)
Final-Recipient: rfc822; [email protected]
Original-Recipient: rfc822;[email protected]
Action: failed
Status: 5.7.1
Remote-MTA: dns; hotmail-com.olc.protection.outlook.com
Diagnostic-Code: smtp; 550 5.7.1 Unfortunately, messages from [84.22.108.221]
weren't sent. Please contact your Internet service provider since part of
their network is on our block list (AS3150). You can also refer your
provider to http://mail.live.com/mail/troubleshooting.aspx#errors
[VE1EUR02FT031.eop-EUR02.prod.protection.outlook.com]

 

Sorry for not answering, but that worked.