[layer8]

There are two issues I ran into after setting up iCloud mail for someone else:

1. Apple’s spam filtering can be very proactive, and the only way to (allegedly) influence it is to move false positives back to the inbox. There are no settings to whitelist addresses (having them in Contacts doesn’t work reliably) or to turn off spam filtering altogether. As often with Apple, you have to accept their design choices of how they think stuff should work, and can’t do much about it.

2. If you’re transferring or forwarding emails from another account, Apple has a 20 MB email size limit while it’s 25 MB for GMail, which means there may be emails that can’t be transferred.

In any case, I would recommend having your own domain and choosing email providers that support custom domains. That way, you can switch email providers at will while retaining your existing email address(es).

[Aerbil313]

Afaik iCloud supports adding custom domains for your mail account, and I am currently looking at something called iCloud Mail Rules in the Settings with which you can apparently define custom handling rules for each sender.