Apple is, of course, scant on details on what iCloud email does as far as spam filtering, whitelisting, and other features. They’re barely even acknowledging the mail or other features coming to iCloud+ right now. According to some websites, you can access the options via beta.icloud.com (does not permanently alter your account for beta access), but the DNS verification steps will fail (it may not be enabled quite yet, since it is a beta).
One tidbit I did find out about iCloud though: Apple DOES NOT encrypt email at rest on their servers. One can imagine that this allows for scanning of email messages via their hashing algos for kiddy porn, or any other reason for that matter…. https://support.apple.com/en-us/HT202303
Considering that email was not ever built with security in mind, and all the current encryption and security protocols were haphazardly bolted on later, would you consider Apple iCloud+ hosted email as an option? What about for business use? I’m considering it, but I also use a personally-hosted E2EE Slack-like chat server on a NAS for secure communications. Running your own email server is a mess. I wouldn’t use email if I didn’t have to for online accounts because you can’t trust the security mechanisms of third-parties, and hosting your own has way too many security hurdles to overcome when it comes to interconnectivity with third-parties, along with external port/exploit scanners constantly hitting your IP (and it has to be a static IP with a PTR record because every spam list on the planet will block dynamic IP ranges).