SAP SD Output/Email Sending a billing document by e-mail

First, your SAP system must be configure by the basis people in order for you to send an external mail.

Whether it can send pdf or other file format will depends on the Mail Server you are using.

The basis people must also maintain the conversion parameters so that SAP knows how to convert the billing documents to be send as a pdf file or other desired format specified by your company.

Finally, you have define the IMG in Maintain Output Determination for Billing Documents (Output type MAIL)