This function can be considered in the following cases
1. I have an account and purchased paid items , But I forgot to log in to the mailbox
2. Can log in successfully , But it was found that the purchase record disappeared , That's because you have multiple accounts , Log in to the account that hasn't bought the course
3. Once bound mobile phone number (2019-6-15 You need to bind your mobile phone number for future registration ), Remember your cell phone number , Can't remember to log in to the mailbox

There is no way in this case
1. No account to buy courses , I can't remember the email address , I have a way , Re register one

Enter the transaction code at the time of purchase , Transaction records in Alipay , Or you can query the transaction code in the wechat transaction record .
Alipay is 2 initial 28 Digit number , Wechat is 4 initial 28 Digit number .

Or enter your mobile phone number (2019-6-15 The mobile phone number is bound only after registration in the future )