From a few hours ago, players cannot use emails from certain providers to register on Minecraft.net; an INVALID REGISTRATION error will show instead.

Some affected providers (incomplete)

• @qq.com
• @foxmail.com
• @sina.com
• @hotmail.com
• @outlook.com
• some custom domains

BTW, QQ is a large email provider in China which has over 300 million users, so this bug has a great impact on Chinese players.