Constant email bounce backs and delivery error

We are having issues with email replies being bounced back as undeliverable or delivery failed. If by chance any of them actually do go through they are put in the recipients spam folders. Here are some of the bounce back messages we are receiving. This is happening from our most used email addresses

heath@delkperformance.com

brent@delkperformance.com

general@delkperformance.com

Please advise on how to fix this. I am continually losing potential customers and creating communication issues with current customers. 

    host hotmail-com.olc.protection.outlook.com [104.47.51.33]

    SMTP error from remote mail server after pipelined sending data block:

    550 5.7.1 Unfortunately, messages from [66.96.189.5] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3140). You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. [BN1NAM02FT026.eop-nam02.prod.protection.outlook.com 2023-05-30T13:09:37.163Z 08DB60CB64F30636]

    host mx1c25.carrierzone.com [64.29.145.41]

    SMTP error from remote mail server after MAIL FROM:<SRS0=5Asg6X=BQ=delkperformance.com=heath@eigbox.net>:

    550 5.7.1 H:SC [66.96.187.3] Connection refused due to abuse. Please see http://spamcop.net/bl.shtml?66.96.187.3 or contact your E-mail provider.