Is anybody try one of these delisting process ??

https://sender.office.com

This one seams to be specifically for live.com and ...

https://support.microsoft.com/en-us/supportrequestform/8ad563e3-288e-2a61-8122-3ba03d6b8d75

https://sendersupport.olc.protection.outlook.com/snds/index.aspx

I did the 2 first one, the first is pretty quick you receive an email and validate if the IP of your server is in their internal block list,
the second is a form is a little bit more elaborate they ask for error message and if you have a website related to that domain.

@jdaviescoates Yeah, removed it from our code for the next release. 5.5 should be out next week.