When a user registers for a QQ account they are given a QQ ID number, and this number is also their QQ email address. This ID number can be bound to another email address, so instead of giving someone your actual email, you just give them your QQ number.

Why are Chinese email addresses numbers?

TIL that many Chinese people use phone-number style e-mail addresses because hanzi characters cannot easily be used, numbers are easier to remember than letters, and their pronunciation can offer other interpretations.

How many numbers is a QQ email?

The account numbers provided for the registered users are selected randomly by the system user registration. In 1995, the registered QQ accounts had only 5 digits, while currently, the digital numbers used for QQ accounts has reached 12.