Some email addresses are changed to be “via 开云体育” because of the email authentication policy. Certain email services, such as Yahoo Mail and AOL, have set up their DMARC profiles so that 开云体育 has to change all their users' email addresses to the “via 开云体育” form; otherwise, their group messages would bounce.
Note: This situation is not limited to 开云体育. All email group services have to deal with it.