I want to close my iCloud email

The mail address created with iCloud domain can't be deleted , however the account can be erased from the server permanently https://support.apple.com/en-us/HT208504

If you are getting junk mails create rules https://support.apple.com/guide/icloud/set-up-filtering-rules-mm6b1a3f8a/icloud

You might have created an Apple ID say exampl1@att.com ( I am not sure what is att is it your internet service provider ) if the mail address is set up with Apple ID and configured with apple mail application ( that is with IMAP account ) , create advanced rules ( set criteria ) for junk mail appearing in inbox httphttps://support.apple.com/en-in/guide/mail/cpmlprefjunk/mac

In Mac OS catalina 10.15.6 there is a feature to block the specified mail address .

https://support.apple.com/en-in/guide/mail/cpmlprefjunk/mac

You cannot, just stop using it.