Select an account, click the "Properties" button in the toolbar to pop up the "Email Account Settings" dialog box, enter the "Stationery" column, and select HTML plain text. Select the following two formats. Then browse and select the desired drawings, and the drawings will pop up, and you will find that the sender's signature can be edited on the stationery. Delete the "sender's signature" and replace it with your own signature, which can be a sentence, your company position, your phone number, or insert a picture, whatever you want.
Save it when you are finished, close the dialog box, and then try to write an email. If not, I will call you!