In case you are interested, it is possible to change your Apple ID Email Address from any third-party Email service provider like Gmail, Outlook or Yahoo to an iCloud based (@icloud.com) Email Address.
If you have been a longtime iPhone user, you might be aware that previously it was not possible to change Apple ID from a third-party based email address (@gmail.com or @outlook.com) to an @icloud.com or other Apple-hosted domain based email addresses (@me.com or @mac.com).
In-fact, now (since, iOS 18.1) you can even go back from iCloud-based Apple ID (@icloud.com) to any third-party based Apple ID (@gmail.com or @icloud.com).
Change Apple ID to iCloud Email Address
Before going ahead with the steps to change your Apple ID to an iCloud based Email Address, you need to be aware that once an @icloud.com email address is added to Apple ID, it will always remain linked to your Apple ID and it cannot be removed.
For example, if you change your Apple ID from john@gmail.com to john@icloud.com, the iCloud based Email Address (john@icloud.com) will remain linked to your Apple ID, even if you go back to using john@gmail.com or john@outlook.com as your Apple ID.
The iCloud based Email Address (@icloud.com) will always remain available under “Reachable at” section of the Apple ID settings screen on your iPhone and it cannot be deleted.
1. Change Apple ID to iCloud Email Address on iPhone
You can follow the steps below to change your Gmail, Outlook or any third-party Apple ID Email Address to an iCloud Email Address on iPhone.
1. Open Settings > tap on your Apple ID Name.

2. From Apple ID screen, go to Sign-In & Security > select your Primary Email Address.

3. On the next screen, select Add New Primary Email Address option.
4. On the next screen, enter the iCloud.com Email address that you want to use as your Apple ID and tap on Continue.

5. If the Email Address is available, Apple will prompt you to move forward with the next steps to complete the process
This way, you can change your current Apple ID from Gmail, Outlook or any third party provided Email Address to Apple’s own iCloud.com Email Address.
Note: You may be prompted to confirm your identity by answering two Security Questions.
2. Change Apple ID to iCloud Email Address Using Mac or PC
You can also change your Apple ID Email Address to an iCloud Email Address by logging in to your Apple Account on a MacBook or Windows computer.
1. Open the Safari browser on your Mac and go to Apple Account page.
2. On the Apple ID website, tap on Sign-in > enter you existing Apple ID and Password to login to your Apple ID Account.
3. Once you are logged-in, tap on your Apple Account card.

4. On the next screen, enter your iCloud Email Address and click on change Primary Email button.

5. If the Email Address that you entered is available, you will be prompted to complete the next steps.