Since Outlook (and any office product really) doesn't have an autostart with Windows option, the only way I've found to have Windows launch Outlook when it starts is to make a shortcut to olk.exe and place it in AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup.
However, the problem with using the Office 365 New Outlook app, is that when it updates, the FQN of the directory changes.
Currently it is C:\Program Files\WindowsApps\Microsoft.OutlookForWindows_1.2023.1108.200_x64__8wekyb3d8bbwe however the version number and 8wekyb3d8bbwe part of it changes each time it updates. This means that eventually I'll stop having Outlook boot with the computer, and I won't realize until I haven't answered e-mails all day.
Why? Why are you like this Microsoft? Just add an option to auto start the app with Windows. It can't be that difficult, you wrote both the OS and the app!