[frontrowseat]

> You might be prompted to add an email account before you can change the setting in Mail. If you don't want to do that, check the preferences of the other email app. You might be able to set a default email app from there.

It says this, but Microsoft Outlook for Mac does not offer that setting. Apple Mail hides the 'Preferences' until you sign in to a mailbox, in which case it immediately downloads your email

[Nextgrid]

True but I don't think it's necessarily malicious - simply a stupid oversight of not being able to access the Mac mail preferences before completing its setup flow. Given that they say this I don't believe there's anything preventing a third-party app (or the command line) from changing this parameter.