Apple hosted email accounts do not work on our site. Those email accounts will be @icloud.com, @me.com, and @mac.com.
Apple deletes our email for no reason, and we have no recourse with them. Apple will remove email from your account without your knowledge, they do not even put them in SPAM for you to decide. See the "Removal of Content" in their terms of service for icloud: https://www.apple.com/legal/internet-services/icloud/en/terms.html
This problem is a well-documented issue with Apple hosted email accounts. We suggest moving to an email provider that does not have a statement like the "Removal of Content" linked above.