Intro
Hi there! 
After a lot of decisions, we’ve decided to block iCloud Mail (@icloud.com) from signing up, the reason we’ve decided to make this change is that there is abuse coming from the “Hide my email” feature.
Keep in mind that if you chose to use a temporary email domain e.g: https://www.mail-tester.com/ you will be blocked, unfortunately, the entire iCloud domain is blocked, so you can no longer use @icloud.com.
My account is signed up with an iCloud address, what do I do!?
Fear not, as we have a solution, those that have registered with an iCloud address will sequentially be notified over time by @system.
Steps to change email.
Head to preferences:
Click on the 
& then “Change Email”:
Once you’ve done this, input a new email, then click “Change”.
We’ve sent an email to your current address. Please follow the confirmation instructions.
Head to your current address and click on the “Confirm New Email link”, then click confirm to change emails.
Then head to your new email and confirm your email there.
Click on the link & confirm the change, and then you’re done!
Please do this as soon as possible!