How can I remove an outdated email address from iCloud Mail?

Hi: Trying to delete an email address - not mine, someone to whom I send emails - from iCloud mail: not mail from the dock mail program. It's an older email no longer in service. Tried clicking on the icon in the mail bar which gives accounts but still cannot find a way to delete that email address. Cannot find anywhere else where that old email address is present; just on iCloud mail page. Help!

[Re-Titled by Moderator]

Original Title: iCloud Email