Microsoft blocked our Business E-mail

Question

Hi. We have 2 business email hosted same server but with different IP. One of them can send message to microsoft emails. i mean *@hotmail.com, *@live.com *@outlook.com.

But from another business email we can not send meesages. More clearly, we are sending but mucrofot server wont accept it. We are getting mail with title: Mail delivery failed: returning message to sender

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. This is a permanent error. The following address(es) failed:

 

 *******@live.ru

    host eur.olc.protection.outlook.com [52.101.73.7]

    SMTP error from remote mail server after pipelined end of data:

    550 5.7.1 Unfortunately, messages from [XXX.X.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]. [Name=Protocol Filter Agent][AGT=PFA][MxId=11BAF66FB897FD65

---

Note that:** I removed receiver email and our server IP address from message

Need help now. how to unblock our server IP?
all https://www.mail-tester.com/ result is 10/10. We have only issue with Microsoft. Hosting providers that all is OK from our side, but as you can see Microfot wont accept our mails