How do I edit the settings for a second iCloud Account in Mail?

I have two iCloud accounts set up in Mail. One for me (using my iCloud account data) and one for my wife (user her iCloud account data). Both accounts are able to send and receive mail. I set up my account first and then set up my wife's account. Everything works fine except that when I go back into the settings (under Preferences) on my wife's account and try to change anything at all, I get an error message saying: "The 'Incoming Mail Server' field cannot be empty", and then it forces me to exit without being able to make any changes. Of course, the Incoming Mail Server field is NOT empty in either my account or hers. Does anyone have an idea of how I can get around this roadblock, or what is going on?