Well now we've just made getting that valuable invoice off to your customer that little bit easier and quicker: we've got a fantastic feature to email the invoice to your customer directly from the Invoice module...
From your invoice, draft invoice, quote, sales or purchase order click on the 'Options' menu and select 'Email' from the drop-down list:
Then fill out recipient name, check the email address and subject line, write a text and click Send
And that's your invoice emailed. Simple, right?