Thunderbird used to work well before v115 except it used to unsubscribe from the folders randomly and still refuses to resubscribe, also no option for calendar syncing in the latest version.
I’ve tried emClient, Spark, Windows Mail app and Outlook so far.
What’s changed with Outlook and iCloud drive for windows is that the option to setup email on Outlook disappeared some time ago. Spark doesn’t have an inbuilt calendar afaik. emClient doesn’t readily support email aliases.
Outlook also has the option of adding an alias from the email compose window, and the received email appears to show the alias on mail app. So far so good. However Outlook doesn’t now sync calendar and contacts even after the option is enabled from the icloud app.
Mail app doesn’t support aliases. Also no calendar or contact sync afaik.
In summary, using icloud email on windows appears to be a pain.