Unable to add icloud account to 'mail'

When attempting to add my icloud email account to mail, I receive the following response:

"The icloud.com IMAP server “Automatically added for iOS & OS X Mail” is not responding. Try checking the network connection, and that the server name is correct. Otherwise, the server might be temporarily unavailable. If you continue, you might not be able to receive messages."

I can receive mail from my other email accounts through 'mail'.....

Ideas?