Apple says: If you created an iCloud account on or after September 19, 2012, your email address ends with @icloud.com. If you created an iCloud account before September 19, 2012, or moved to iCloud with an active MobileMe account before August 1, 2012, you have both @me.com and @icloud.com email addresses. If you had a working @mac.com email address as of July 9, 2008, kept your MobileMe account active, and moved to iCloud before August 1, 2012, you can use @icloud.com, @me.com, and @mac.com email addresses with your iCloud account.
For corporate email, Apple's email domain in apple.com. They don't appear to use localized email domains like apple.co.uk or apple.fr. They do use sub-domains under apple.com (like support.apple.com) for various services, including email. But they have a wildcard MX record for all sub-domains, so it's not easy to tell what's valid or not. That might mean they accept misdirected mail to sub-domains and use it to feed their spam filtering (spamtraps).