Sorry, nope. It was my own idea (to best of my memory, I haven't seen this anywhere else, so I think it was an original one), I've tried it out, it worked, but I never finalized it, nor wrote anything about it.
It wasn't anything complicated, though. I've just did the documented steps to set up Outlook with my own domain (not sure if that's a free option, I have MS365 subscription for Office apps), except that I made no changes that would disrupt my existing mail system - I've added to SPF and DKIM instead of setting/replacing them, and I haven't touched any MX records at all. Then I've just grabbed Outlook's SMTP details and sent a test email to my other test Outlook account via SMTP and it got delivered with my email address, which gave me a confirmation that my idea had actually worked. I haven't really updated my MTA to do the routing thing, as I was about to replace it anyway (I did since then, replaced Postfix with Maddy).
It wasn't anything complicated, though. I've just did the documented steps to set up Outlook with my own domain (not sure if that's a free option, I have MS365 subscription for Office apps), except that I made no changes that would disrupt my existing mail system - I've added to SPF and DKIM instead of setting/replacing them, and I haven't touched any MX records at all. Then I've just grabbed Outlook's SMTP details and sent a test email to my other test Outlook account via SMTP and it got delivered with my email address, which gave me a confirmation that my idea had actually worked. I haven't really updated my MTA to do the routing thing, as I was about to replace it anyway (I did since then, replaced Postfix with Maddy).