Microsoft's email service consists of
live.com domains. As this is a very popular email service, you may eventually experience an issue within your server/network that resorts in you getting blocked by Microsoft due to undesirable email habits. This could be due a number of things.
When you do find yourself blocked, you may see some error messages such as:
550 SC-004 Mail rejected by Outlook.com for policy reasons. A block has been placed against your IP address because we have received complaints concerning mail coming from that IP address. We recommend enrolling in our Junk Email Reporting Program (JMRP), a free program intended to help senders remove unwanted recipients from their email list. If you are not an email/network admin please contact your Email/Internet Service Provider for help.
550 5.7.1 Unfortunately, messages from [xx.xx.xx.xx] 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. [HE1EUR04FT063.eop-eur04.prod.protection.outlook.com]
The removal process for this is quite simple, you simple need to follow the steps listed below:
sendmail(php) lines from your websites.
If your blacklist has not been removed you will need to resolve anything they have identified or reply back to them asking why it cannot be lifted and they will provide you with a reason.