The steps are as follows:

Open QQ mailbox and log in.

After logging in, find "Settings" on the email home page and click Enter.

Find "General" in the mailbox "Settings"

Find Personalized Signature in General, and then Add Personalized Signature.

Then create a new personalized signature in the page, and finally click OK.

Then it was set successfully.

According to the specific types of problems, step disassembly/cause principle analysis/content expansion, etc.

The specific steps are as follows:/The main reasons for this situation are ...