How to change your Apple ID to a different email address
Go to appleid.apple.com and sign in.
In the Account section, choose Edit.
Choose Change Apple ID.
Enter the email address that you want to use.
Choose Continue.
If you changed your Apple ID to a third-party email address, check your email for a verification code, then enter the code. Learn what to do if you didn't get the email.
If you use services like iCloud or Messages to share with friends and colleagues, sign in to those services with your updated Apple ID.
If your Apple Mail doesn't seem to be searchable and/or has become so slow it seems to hang your Mac - or even displays incorrect email content, then it's time you attacked the problem: it's time. In the Mail app on your Mac, choose Mail Accounts. Select the account, then deselect the Mail checkbox. Now the account’s messages are not shown in Mail. To use the account again with Mail, select the Mail checkbox; the account’s messages are shown again (they don’t need to be downloaded from the server again).
The only way to get Mail.app as far as to reload the data from the IMAP server seems to be to remove the account and recreate it. Now, here the fun starts. First Mail.app redirects me to iCloud settings, even if Mail has not been selected in iCloud settings (as managing Mail settings that way destroys proper settings, so all accounts also.
If you can't change your Apple ID
If you try to change your Apple ID to an @icloud.com email address that was created within the last 30 days, you will be asked to try again later.
If you see a message that the email address you want to use isn't available or is already in use, check that you or a family member aren't already using that email address with a different Apple ID. If a family member is using that email address, remove it from their account then try to use it. Istat for windows.
In some countries or regions, you can use your phone number as your Apple ID. But if your Apple ID is an email address, you can't change it to a phone number.
To switch to a different Apple ID account—not change the email address that you use as your Apple ID—you can sign out, then sign in with a different Apple ID.
Learn more about how to use your Apple ID and keep your account information up-to-date.