[Bug] Hotmail bouncing mails [Solved]

When players try to validate hotmail email addresses, they bounce back with the message:

<[XXXX@hotmail.com](mailto:XXXX@hotmail.com)>: host
hotmail-com.olc.protection.outlook.com[104.47.8.33] said: 550 5.7.1
Unfortunately, messages from [185.189.51.110] 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.
[AM5EUR03FT034.eop-EUR03.prod.protection.outlook.com] (in reply to MAIL
FROM command)

The host that I use seems to have gotten some other IP in the same range as the mucklet.com VPS’ IP (185.189.51.110) black listed, which affects us as well.

I will try to contact Microsoft as suggested in this Microsoft Answers topic to see how to best resolve it.

I brought the issue up with Outlook.com Deliverability Support.

They have responded:

We have implemented mitigation for your IP (185.189.51.110) and this process may take 24 - 48 hours to replicate completely throughout our system.

So, hopefully we are rid of this issue.
I haven’t had any similar errors recently either.