What does the red name of the qq mailbox recipient mean?

Qq mailbox recipient's name is red, indicating that the recipient's address is incorrect.

1. If the recipient is a qq mailbox, write the qq number when the recipient's address comes out, without adding @ qq.com. ..

2. If it is an account other than qq mailbox, as shown in the figure, several common mail formats are listed, so you need to add the domain name of the corresponding mailbox.