A signatur is added to each email you send from the CRM system automatically, if the signature has been stored at Settings -> Users ->your user edit view. Such an email can get easily formated by the HTML format by using CRM tools.
Goto the detail view of one contact stored at your CRM. Click on the action “send mail”. In the window which opens you may enter your signature and design it with the tools provided. When finished click the Icon “display source code” (Quellcode). Copy the content and enter it in your signature field at a users settings.