Function finish 

pub fn finish(
    sign_in: SignIn,
    client_id: &str,
    address: &str,
    stop: &AtomicBool,
) -> Result<Grant, SyncError>

Waits for Microsoft’s answer (five minutes at most, or until stop), trades its code for tokens at once (a code lasts about a minute), reads who signed in and whether the account is a personal or a work one, and keeps the grant in the keyring under address. The access token is kept in memory. Who signed in is not checked against the address here: an alias, a shared mailbox, a phone number’s sign-in differ; the mail server’s own login decides (the window’s outlook.rs).