This is impossible as clearly stated on Apple's website:
How to change your Apple ID if it ends with @icloud.com, @me.com or @mac.com
If you use an @icloud.com, @mac.com or @me.com email address as your Apple ID, you can’t change it to a third-party email address.
That is your Apple ID so you can't change it, the only real alternative is to create a ...
To implement server side rules, your server must support it.
There’s nothing in Apple Mail that can enable something on the server if the server doesn’t support that feature.
I searched Cox’s Support site for “server side rules” and found nothing. Additionally, I found this message
Cox Email is a free service that was included with all Cox High ...
You can't remove the email functionality from a icloud.com or me.com adress. What you can do instead is to
log into icloud.com in any browser
go to Mail
click on the cog wheel at bottom left and select Settings (first entry in the menu)
set auto-forwarding of all mails to your new email adress
You may need to rebuild a mailbox to update the list of messages it contains. For example, if messages appear to be missing or garbled, or if you can’t find all relevant messages when you search using the Entire Message search option.
In the Mail app on your Mac, select a mailbox in the sidebar.
Choose Mailbox > Rebuild.
When you rebuild mailboxes for ...
It is possible to choose which mail to use in Sign in with Apple :
First go to Settings > Your Apple ID > Name, Phone Number, Emails > Make sure the email you want to use is added.
Open the app and click Sign in with Apple and then click on Share my Mail.
It will then propose you which mail associated with you Apple ID you want to use.
Note that it doesn't ...
It's called an email alias.
Create or change an alias
In the Mail app on your Mac, choose Mail > Preferences, then click Accounts.
Select an account, then click Account Information.
Click the Email Address pop-up menu, choose Edit Email Addresses, then do one of ...
I tried Speaking Email (speaking email website link) and am finding it really great. It's a one by one email reader which keeps it nice and simple. It has commands like "delete", "reply" and so on which are voice commands, a nice idea - really powerful and no need to wear your eyes out peering at a screen.
The reply dictation works well. It is best for ...
I know this is old but I just had this happen to me on iOS 13. I was trying to mark all email as read and slipped and marked everything as junk... After correcting that nightmare, I noticed my email showing on my phone was very old. I read the solution here about restoring the phone from the backup and I did not want to do that. So the solution I came up ...