apple mail configuration for iCloud email address

BIG problem with configuring a macbook pro email account.

no problem with the gmail accounts, not even with the live accounts.

no problem with 3 of the .mac accounts, but the 4th one ...

i always get the incoming mail server empty and dimmed - and can t fill it in manually.

i ve deleted the email address, tried to do it manually etc. to no avail.

anyone can help?????