https://support.apple.com/en-asia/guide/icloud/mme8ed800b5d/icloud
Personalize iCloud Mail with a custom email domain and share with others - Apple Support
Get an overview of how you can use a custom email domain to personalize your iCloud Mail addresses.
custom email domain
https://support.apple.com/en-bw/guide/icloud/mm043dbc8d94/icloud
Transfer custom email domain addresses on iCloud.com - Apple Support (BW)
On the iCloud+ Features page on iCloud.com, you can transfer addresses between members of your iCloud Mail custom email domain.
custom email domainapple supporttransferaddresses
https://support.apple.com/en-lamr/guide/icloud-iphone/mm043dbc8d94/icloud
Transfer custom email domain addresses on iCloud.com - Apple Support
On iCloud.com, you can transfer addresses between members of your iCloud Mail custom email domain.
custom email domaintransferaddressesicloudapple
https://support.apple.com/en-eg/guide/icloud-ipad/mm043dbc8d94/icloud
Transfer custom email domain addresses on iCloud.com - Apple Support (EG)
On iCloud.com, you can transfer addresses between members of your iCloud Mail custom email domain.
custom email domainapple supporttransferaddresses