Create and customize your Yahoo Mail signature using NEWOLDSTAMP Editor.
After you have created your NEWOLDSTAMP signature follow these simple steps to set it up in Yahoo Mail.
Select Yahoo Mail tab below the Signature preview.
Press Select Button and copy your signature to Clipboard (Ctrl+C or Command+C).
Go to your Yahoo and (right top corner) click on Settings → Accounts.
In Email addresses section choose Yahoo.
Scroll down and click the checkbox near “Append a signature to the emails you send”.
Insert your signature into edit area (Ctrl+V or Command+V) and click Save.
Congratulations! Now you will see your new signature in every email you send with Yahoo.