This is a common issue with Office 365 / Hotmail / Outlook. You’re in good company in their spam folder. To test out delivery to their service, we created an Office 365 account ourselves. On first login, we found an email that they sent us welcoming us to the service. Guess where that email was? The spam folder. See for yourself:
How can you expect any consistency in arriving in the inbox when the people who made the inbox can’t even get their emails there? You can’t, but there are things you can do to help your chances.
You do your best by making sure that you get a 10 out of 10 score from mail-tester.com. It’s simple: Go to mail-tester.com, copy the email address given to you, send an email to it, wait a few seconds, then click the button to check your score. We can’t help your content or domain reputation, but your DNS can get a 10 out of 10 by using our DNS tutorials.
Microsoft has an article published about reporting false positives to them:https://docs.microsoft.com/en-us/microsoft-365/security/office-365-security/submit-spam-non-spam-and-phishing-scam-messages-to-microsoft-for-analysis?view=o365-worldwide