Hello. The e-mail address filled in the credit card is your registered e-mail account. First, you need to download an email address. You can download the mailbox master. After downloading, the mailbox owner chooses the mailbox domain name to register the mailbox. (e.g. 126 mailbox. 136 mailbox, etc. ). You can register with pinyin letters when you register. You can also register with Pinyin and Arabic numerals. After the registration is completed, the mailbox can send and receive emails. You can also use an email account to register applications. The registration number is your email account. This is your email address, too. When applying for a credit card. Just fill in your email account number in the email field.