This sounds similar to my experience with Microsoft based email (Outlook, Hotmail, Live, custom 365 domains) I eventually decided to route Microsoft hosted emails over Amazon SES instead of a VPS hosted Postfix setup. This did help a bit. The fact that all other email providers work perfectly fine and Microsoft is the problematic one I think signals an issue with their spam filtering.
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This sounds similar to my experience with Microsoft based email (Outlook, Hotmail, Live, custom 365 domains) I eventually decided to route Microsoft hosted emails over Amazon SES instead of a VPS hosted Postfix setup. This did help a bit. The fact that all other email providers work perfectly fine and Microsoft is the problematic one I think signals an issue with their spam filtering.