If you want a reliable way of sending mail to Hotmail or any other Microsoft free email services you will need to use a 3rd party mail service.
As they are now blocking all IP's in blocks of /24 that have no business ending them email i.e. not configured for mail according to their own very strict criteria when only a few are marked as spam or unsolicited through automation or human intervention for the whole range and they will not delist an IP when it has no business sending them mail i.e. their scans upon submitting a mitigation request show that an IP is not setup to their own standards for mail which is why the IP you may have never used for mail does not qualify for mitigation or may be blacklisted with them despite the fact that they confirm it has never sent mail to them.
You need to have a literally perfect mail server setup first in order to qualify to be able to send email to them however you would only have an issue if your mail server was not set up properly and now you are already blacklisted, in some cases, they may white list your IP once you correct any issues, there is nothing Inception Hosting can do to influence this unlike with almost all other blacklists as Microsoft insist the mail server operator manages the delisting process which is problematic but never the less this is how Microsoft is choosing to operate.
The specifics of what gets IP blocks 'blocked' is not always human-driven either, it could be a person marking mail as unwanted/junk or it could just contain many links or fail on some other checks like none matching PTR records or if you do not have spf+dkim configured as they expect it (the last one is a big one).
Either way, they expect the end-user i.e. the person or company directly using the IP to be the one to make the case for individual delisting, the link for delisting: https://support.microsoft.com/en-us/getsupport?oaspworkflow=start_1.0.0.0&wfname=capsub&productkey=edfsmsbl3 while they may list a whole /24 for very minor reasons they will only delist a /32 at a time when they are satisfied you have ensured you are not sending unwanted mail and have a properly configured mail server if they initially refuse to delist your IP (common) you will need to escalate it yourself as you are the only one that can actually provide the required information and make the changes to your server they want.
Before escalating please make sure:
Your PTR record matches your sender's domain.
You have spf configured.
You have dkim configured.
Your emails that are sent to Hotmail or any other Microsoft free mail service are NOT sent by ANY automated process such as forum notifications, WordPress or other site login confirmations, any contact form that sends an auto-response or literally any function at all on your server that could potentially send an email to Microsoft domains i.e. they are all hand-typed only.
A very common cause is a website that allows registration, it only takes a few spam bots to try to register on your site with fake @hotmail.com addresses which will then cause your server to send emails to none existing emails to get your server blacklisted.
The whole situation with Microsoft is getting so ridiculous that there is almost no guarantee of delivery to Microsoft free email services from 3rd party email servers due to their policy's.
The obvious workaround is to use a Microsoft account or even a Gmail as an SMTP relay for Microsoft domains, it is fairly trivial to do through EXIM routing and would certainly take less time to implement than trying to work with Microsoft so that is the recommended way forward.
Changing your IP will make no difference or be a very short term fix as the sending domain will not change nor the sending pattern.
