Emails Not Sending to Hotmail.com?

Everytime I try to send an email to a hotmail.com account I get the following error:

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.

XXX@hotmail.com, ERROR CODE :550 - 5.7.1 Unfortunately, messages from [103.138.129.23] 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. [BN8NAM04FT057.eop-NAM04.prod.protection.outlook.com 2023-11-09T07:34:26.861Z 08DBE097DB74E5E5]

Also I have noticed a tonne of my emails are going straight to spam even though they are normal everyday emails. I cant send emails to clients in hotmail, even if I do half of them go to spam... I need a fix asap.

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