Do you want to create a different signature for reply emails?
Start in a newly composed email, and click on the Signature button, Include group, Message tab. Click on the Signatures … selection from the dropdown menu. After clicking on the New button, create your “reply only” signature. Click Save. Select in from the dropdown list in the replies/forwards: field. Be sure you also have the desired signature in the New messages: field above it. If you use more than one email address, you can set different signatures for each one.