I just attempted to send email from my web hosting account to a Hotmail account and got the following message:
The email address below is not real (because this is a public forum). However, I was using my actual email hotmail address.
This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of
its recipients. The following addresses failed:
SMTP error from remote server after MAIL command:
550 OU-002 (SNT0-MC1-F7) Unfortunately, messages from 18.104.22.168 weren't sent. Please contact your Internet service provider since part of their network is on our block list. You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors.