What is the format of Apple's mail?

Apple's icloud email format is an email address with the suffix @ icloud.com. If you have an iPhone or iPad, you can create a free iCloud email address for free.

Only one iCloud account ending in @ icloud.com can be created per device. In addition to services for Apple, your iCloud account can also be used as an email address with the suffix @ icloud.com.

Extended data:

Create an Apple ID? You need to enter an email address. This email address is your Apple ID and the user name you use to log in to Apple services such as iTunes and iCloud. It is also the contact email address of your account.

You can use your own qq email, usually QQ number plus @qq.com, or you can use Netease email, Gmail and so on to register.

References:

Baidu encyclopedia -icloud