I had a promising experience yesterday with the “New Outlook” (the one you can toggle on at the top of the app window). I was trying it out along with the Todoist plugin, and was pleasantly surprised to find that the Todoist plugin creates a task in Todoist that links back to the Outlook message across devices — sort of. I say “sort of” because when you click the link, the linked Outlook message opens in a web browser (the web version of Microsoft 365, in my case), not the Outlook app.
This isn’t ideal, but it is completely workable for me. I can use the new Outlook Mac app for most of what I do, except for those instances where I need to call up a message (in which case the message loads in a browser).
This link even works across my devices (iPhone included) in my limited testing. You still can’t move a message to a new folder without breaking the link.
I don’t have the know-how to see how Todoist is doing it, as there are no user-exposed links in the new Outlook. I suspect the app might be a web wrapper of some sort, but if someone were to figure this out and bring it into Hook, I would forever be in awe.