If you want to add your signature to all out going messages through Yahoo Mail .
Take a look how to do it.

  • First Sign in to your Yahoo Mail with Your username and Password
  • Then click the Link click here which Beside finger Print Symbol which open a new tab ,then enter the name or website you want to use as a Signature to all outgoing Messages.
  • When you Enter your Signature Click Save and click Back to mails,When ever You send a message make sure ADD MySignature is enabled .