It stuff: Hotmail, Outlook, Outlook 365 and Junk mail issues

Do you run your own mail server, but any email you send to hotmail.com, outlook.com or other Microsoft hosted domains is sent to the 'Junk' folder?
I run my own mail server, which is configured exactly as per Microsoft's guidelines in their various support documentation.
However, despite several attempts at getting "mitigation" implemented for my mail server IP address, Microsoft are unable to explain why my email continuously ends up in the end users' Junk folder.
Back in June 2021, they responded to my support request, stating that mitigation had been implemented for my mail server IP address.
Fast forward a few weeks, and still my email went to the Junk folder (even with accounts I had not sent email to previously).
My IP address is a proper static IP on a hosted server. It is not listed in any blacklist, at least for the past three years that it's been assigned to me - and I'm not aware of it being listed previously.
I have SPF records, sign my emails with DKIM, use MTA-STS, and all DNS records are 100% correct.
Every request to Microsoft for support results in the same rhetoric - I am referred to their "enhance_deliver.pdf" document (which has several errors and typos).
I signed up to their SNDS "Smart Network Data Services" service to check for spam reports related to my IP address (although I don't send enough email to these domains, those that I do send email to are regular contacts).
There was a moment of considerable irony, when my email system tagged their SNDS confirmation email as spam. Why? Well the 'HELO' name didn't match the IP....
So seemingly at the end of the day, with Microsoft it's a case of "don't do as we do, but do as we say - and if you're lucky, we won't send your email to Junk".
On a final note - their support team constantly recommended that I sign up to (and pay for!) a Validity subscription. Why would I want to do that when my systems are configured 100% anyway?
Do Microsoft have a vested interest in Validity?
I have no problem sending email to any other provider. Gmail, AOL, Yahoo etc. all work just fine. It's only Microsoft.
Perhaps all their "smart" this and "smart" that is not so smart after all...