Website email arrives at Gmail and other domains but not Hotmail.com or Outlook.com
I have a domain for example https://example.com website setup on a DO VPS. I have configured the VPS to be the primary MX for the domain and configure what I believe is an appropriate SPF record for it. The VPS is running postfix and can send and receive email for the domain. I can receive email fine to multiple other domains.
I also note that a similar question has been asked before but the work-a-round was performed by the person adding the email address to the safe senders list using outlook.com web interface. This is unsuitable for my purposes because the emails need to arrive at outlook.com or hotmail.com mailboxes without intervening.
Has anyone got any information that could allow me to get to the bottom of why hotmail / outlook.com aggressively blocks valid email while hiding behind many pages of policy documents that don't enlighten me as to why I have an IP address designated as "Not qualified for mitigation".
I have attempted to engage with Microsoft regarding how to go about getting it working but if anyone has any experience with getting a Droplet to email directly to mx*.hotmail.com MX servers and have the email accepted I would love to hear from you.