Sending invoices automatically / Custom fields on order conf

Hi,

is there a way to send out invoices automatically by mail?

At least in Germany I have to send the disclaimer and the terms by mail to a customer. I've put the required legal texts in the additional fields of the invoice. But I don't see how I can send the invoice automatically by mail. 

It would be great to have that option, or offer similar fields on the order confirmation, which is automatically sent.

Best regards

Hans-Joachim