There are a two areas where you can manually send invoice the emails out of the system:
Once the invoice is finalized, at the top right you will see the "Email" button.
From Invoicing Management you can click the envelope icon next to a finalized invoice.
Automatically send invoice emails upon Finalizing via the Client Portal:
If you have invited clients to your Client Portal and those contacts have accepted their invite, an email will automatically be sent to them upon finalization. Click here to learn more.
**Note: You can also view email history through the "Send Invoice" box by clicking on the "Email History" tab. You can also view the history by running an "Invoice Email" report.