emails bouncing

I would appreciate if someone could help me with emails bouncing again.  

I have been told to get a new hosting  service or I will loose an account.

I receive emails ok but when I send emails to one company I get a bounce.  It appears their server is blocking me.

Message

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:

    host xxxx.com.mail.protection.outlook.com []

   SMTP error from remote mail server after RCPT TO:<    xxx.com>:

    550 5.7.1 Service unavailable, Client host [66.96.184.5] blocked using Customer Block list AS(1420) [HK2PEPF00006FAE.apcprd02.prod.outlook.com 2024-08-12T23:01:44.315Z 08DCB6FB6FDF9D28]