Inserting signature in Mail form from outgoing email

Hi,

I'm trying to send outbound email from service request in SAP CRM. When I select send mail the mail form is displayed. We have option to attach the document, priority and sensistvity. Along with this we also have option to save signature. Once I save the signature how to insert the signature into mail form so that I can send the signature with the mail form.

Thanks

Vinod