Someone hacked into on of our website's email addresses to send spams since 31 Jan 2019 and we only found out on 4 Feb. Why? Cos we set the password of the email to be 123456. My bad. But we have fixed this and all blacklisting servers are no longer blacklisting us. Except for Microsoft.
When we sent emails to hotmail.com or outlook.com email addresses, we still get "550 5.7.1 Unfortunately, messages from [xx.xxx.xx.103] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3150)".
We submitted the support request for removal for 4 times at https://support.microsoft.com/en-us/supportrequestform/8ad563e3-288e-2a61-8122-3ba03d6b8d75 and below is all we got.
Please note that your ticket number is in the subject line of this mail.
Note: Errors are unlikely, however, if an error is indicated, please resubmit the specific IP or IP range.
Our emails are still being blocked. How do I fix this?