@chris I did that for a year or so as well, but often enough, the iCloud servers were blocked from either sending to certain domains or receiving from them. I'm on a number of groups on groups.io, and iCloud mail was frequently having trouble with that provider, or vice versa. I moved my mail domains to a hoster here in Germany which is very data privacy friendly and only costs me a few Euros per month. It's called @mailbox_org. And I cannot praise them enough. The offering is very good and uses open source and open standardts, and it works reliably for me and never gives me any trouble.