When you do find yourself blocked, you may see some error messages such as:ĥ50 SC-004 Mail rejected by for policy reasons. Suspicious email patterns because of newsletters.No opt-out subscription for newsletters.As these are very popular email service,s you may eventually experience an issue within your server/network that resorts in you getting blacklist by Microsoft due to undesirable email habits. Microsoft’s email service consists of, , msn.com and  domains.

I got unblocked, but how can I prevent from being put on blacklist again?.