Auto mail generation in billing document
I am facing a problem in automatic generation of E-Mail during billing. The scenario is that whenever the user saves a billing document an e-mail will generate automatically and notify the customer about the materials billed and the value of the invoice. The e-mail address will be stored in the customer master record of the payer. Now the problem is that in which form routine i will attach this mail generation programme so that this mail is automatically generated when the billing document is saved. Or else you can also suggest me how to configure this procedure.