My guides here and here talk through the general process for reaching out to Microsoft to request unblocking, but in a scenario where you're newly sending from your IP address, or you're going through IP warming, be sure to request "pre-emptive accommodation" from Microsoft. Where you do this is in response to the reply you receive from "Hotmail Sender Support," after submitting your unblock request via their online form.
Using the magic phrase "pre-emptive accommodation" tells Microsoft that this mail stream is newly coming from this IP address. You're asking for them to give you some time to build up reputation. They'll respond, asking you for data on your projected email send volume for the near term. Provide this to them. They'll use it to decide how much mail to allow from your sending IP address, and it means that if you stay generally within the volume guidelines you tell them, your chances of getting blocked will be reduced.
Of course, it doesn't mean it's open season to spam away. They're not shutting off the spam filters. And Microsoft can be quick to block. Sometimes intentionally so, sometimes not. Reputation still applies here, so make sure you're sending wanted mail, and that you're paying attention to spam complaints and reputation data from JMRP and SNDS.