Problem saving email preferences for new iCloud email address

Question

I was trying to enter a new email address for iCloud in the Apple Mail program and after clicking save I receive the following message,"Writing your preferences to disk has failed. Your preferences may not have been saved. The permissions on ~/Library/Preferences may be wrong or your disk may be fullI'  I know the disk is not full on my new MacBook Pro. I went into LIbrary/Preferences but could not find the mail preferences.
The preferences have not been saved because every I time I start the computer the new email is missing from my email preferences.
Thanks for your help.

Answer 1

While you can't currently change your Apple ID to a Mobile/iCloud email address, I found a solution that helps with a related problem.
Suppose you've recently got an iCloud email address, but Apple are still sending all your iTunes Store, App Store and Mac App Store receipts to your old gmail address (the one that's still your Apple ID). And suppose they're also sending all the Apple Support Communities notifcation emails to your old gmail address. How do you change it? How do you fix it?
Well the option exists, but it is hidden away in a weird place. To get Apple sending all of their receipts and notifications to your new iCloud email address...
• Go to your country's Apple Store website http://store.apple.com/
• Click on the Account button in the top-right corner
• Under Account Settings, click on Change your default shipping or billing info
• Sign in with your usual Apple ID and password
• The email address listed under Payment Information is the key
• Click on Edit next to Payment Information and change that email address to your iCloud address
That's all you have to do.