I returned to QQ, and there was a message about it.

This is the offline message receiving function of QQ. If you don't want to accept offline information, you need to log out of your QQ account when you quit QQ software.

To cancel an account:

Open the QQ software of mobile phone, click the avatar in the upper left corner, and then select the setting option;

Select account management under settings;

Continue to choose to exit the current account, and then close the QQ software to cancel the message prompt.

If you want to restore the offline message receiving function, just log in to QQ directly, and don't cancel your account before closing the software.