As of Thursday, October 15th, 2020, we became aware that users across a variety of Apple-managed email URLs, including @icloud.com, @me.com, and @mac.com, were having difficulties receiving emails from us due to a system block.
Our engineering team is working with the iCloud email admins to resolve this issue as soon as possible. In the meantime, we would recommend, if you're able, changing your Discord email, and if you're unable, write in a support ticket at https://dis.gd/contact so we can let you know when the issue is resolved.